User:Ben Dawson/Sandbox1 - Revision history

Ben Dawson at 21:08, 23 April 2018

2018-04-23T21:08:19Z

←Older revision		Revision as of 21:08, 23 April 2018
Line 2:		Line 2:

	== Background ==		== Background ==
-	The Human Poly(A) Binding Protein [https://www.rcsb.org/structure/1cvj (PABP)] was discovered in 1973 by the use of a sedimentation profile detailing the RNase digestion differentiated the PABP protein. <ref name="A Protein of Molecular Weight 78,000">Blobel, Gunter. “A Protein of Molecular Weight 78,000 Bound to the Polyadenylate Region of Eukaryotic Messenger Rnas.” Proceedings of the National Academy of Sciences of the United States of America, vol. 70, no. 3, 1973, pp. 924–8.</ref> Attempts to purify the 75 kDa protein then followed~~. In~~ 1983, then considered “poly(A)-organizing protein,” was determined and purified by molecular weight, ligand-binding affinity, and amounts found in cytoplasmic portions of cell with ability to bind to free poly(A). <ref name="Cytoplasmic Poly(A)">Baer, Bradford W. and Kornberg, Roger D. "The Protein Responsible for the Repeating Structure of Cytoplasmic Poly(A)-Ribonucleoprotein." The Journal of Cell Biology, vol. 96, no. 3, Mar. 1983, pp. 717-721. EBSCOhost. </ref>	+	The Human Poly(A) Binding Protein [https://www.rcsb.org/structure/1cvj (PABP)] was discovered in 1973 by the use of a sedimentation profile detailing the RNase digestion differentiated the PABP protein. <ref name="A Protein of Molecular Weight 78,000">Blobel, Gunter. “A Protein of Molecular Weight 78,000 Bound to the Polyadenylate Region of Eukaryotic Messenger Rnas.” Proceedings of the National Academy of Sciences of the United States of America, vol. 70, no. 3, 1973, pp. 924–8.</ref> Attempts to purify the 75 kDa protein then followed, where shortly after, in 1983, then considered “poly(A)-organizing protein,” was determined and purified by molecular weight, ligand-binding affinity, and amounts found in cytoplasmic portions of cell with ability to bind to free poly(A). <ref name="Cytoplasmic Poly(A)">Baer, Bradford W. and Kornberg, Roger D. "The Protein Responsible for the Repeating Structure of Cytoplasmic Poly(A)-Ribonucleoprotein." The Journal of Cell Biology, vol. 96, no. 3, Mar. 1983, pp. 717-721. EBSCOhost. </ref>


-	PABP is a mRNA binding protein that binds to the 3’ Poly(A) tail on mRNA. It is comprised of four [https://en.wikipedia.org/wiki/RNA_recognition_motif RNA recognition motifs] (RRMs), which are highly conserved RNA-binding domains.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The RRM in PABP is found in over two hundred families of proteins across species, indicating that it is ancient.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Through extensive Adenosine recognition by the RRMs of PABP, the protein is involved in three main functions: recognition of the 3’ Poly(A) tail, mRNA stabilization, and eukaryotic translation initiation. ~~The~~ contributions of controlling gene expression ~~via~~ different families of PABPs is not yet fully understood. PABP families are divided into nuclear and cytoplasmic. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref> PABP1, which is predominantly cytoplasmic, is often referred to as PABP because it is the only form of PABP that has been extensively studied in its role with mRNA translation and stability. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref>	+	PABP is a mRNA binding protein that binds to the 3’ Poly(A) tail on mRNA. It is comprised of four [https://en.wikipedia.org/wiki/RNA_recognition_motif RNA recognition motifs] (RRMs), which are highly conserved RNA-binding domains.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The RRM in PABP is found in over two hundred families of proteins across species, indicating that it is ancient.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Through extensive Adenosine recognition by the RRMs of PABP, the protein is involved in three main functions: recognition of the 3’ Poly(A) tail, mRNA stabilization, and eukaryotic translation initiation. However, the contributions of controlling gene expression throughout different families of PABPs is not yet fully understood. PABP families are divided into nuclear and cytoplasmic. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref> PABP1, which is predominantly cytoplasmic, is often referred to as PABP because it is the only form of PABP that has been extensively studied in its role with mRNA translation and stability. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref>


Line 56:		Line 56:

	===mRNA Stabilization===		===mRNA Stabilization===
-	PABP prevents the deadenylation and decapping of the mRNA~~, serving as a source of stabilization~~. Poly(A) ribonuclease [https://en.wikipedia.org/wiki/Poly(A)-specific_ribonuclease (PARN)] work to deadenylate mRNA, but the presence of PABP ~~prevents~~ its ~~activity~~. The PABP protein is able to protect mRNA degradation through the complex that it forms with the elongation initiation factors, which prevent deadenylation and decapping due to their presence.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> This has been verified by the presence of deadenylation products and the comparative size of PABP footprints. There is some evidence indicating that PABP is involved in the prevention of endonucleolytic cleavage; however, only a small amount of mRNA is degraded from endonucleolytic cleavage, so it is not widely researched.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>	+	Serving yet again as another sourc of mRNA stabilization, PABP prevents the deadenylation and decapping of the target mRNA. Typically, Poly(A) ribonuclease [https://en.wikipedia.org/wiki/Poly(A)-specific_ribonuclease (PARN)] work to deadenylate mRNA, but the presence of PABP hinders its function. The PABP protein is able to protect mRNA degradation through the complex that it forms with the elongation initiation factors, which prevent deadenylation and decapping due to their presence.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> This has been verified by the presence of deadenylation products and the comparative size of PABP footprints. There is some evidence indicating that PABP is involved in the prevention of endonucleolytic cleavage; however, only a small amount of mRNA is degraded from endonucleolytic cleavage, so it is not widely researched.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>


Line 63:		Line 63:
	Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.		Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.

-	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3).¹ Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> [[Image:closedlooper.png\|300px\|left\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]] The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>	+	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3). Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> [[Image:closedlooper.png\|300px\|left\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]] The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>

	In more complex eukaryotic organisms, PABP indirectly stimulates translation via [https://en.wikipedia.org/wiki/PAIP1 PAIP-1] (PABP interacting protein). A higher presence of PAIP-1 increases the rate of translation initiation, indicating another way to “close the loop.”¹		In more complex eukaryotic organisms, PABP indirectly stimulates translation via [https://en.wikipedia.org/wiki/PAIP1 PAIP-1] (PABP interacting protein). A higher presence of PAIP-1 increases the rate of translation initiation, indicating another way to “close the loop.”¹
Line 72:		Line 72:
	===Oculopharyngeal Muscular Dystrophy===		===Oculopharyngeal Muscular Dystrophy===

-	Oculopharyngeal muscular dystrophy, or [https://rarediseases.info.nih.gov/diseases/7245/oculopharyngeal-muscular-dystrophy OPMD], is an autosomal dominant late-onset disease. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> ~~It’s~~ characterized by the myopathy of the eyelids and the throat~~. The~~ symptoms ~~entail~~ eye-drooping and difficulty swallowing. There are two types of OPMD: autosomal dominant and recessive, both originating from the mutation of the PABP nuclear 1 [https://en.wikipedia.org/wiki/PABPN1 (PABPN1)] gene located on the long arm of chromosome 14. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> This mutation results in an abnormally long polyalanine tract, 11-18 alanines, opposed to the normal 10. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> Patients with longer PABPN1 expansion (more alanines) are on average diagnosed at an earlier in life than patients with a shorter expansion; therefore, expansion size plays a role in OPMD severity and progression. <ref name="“Correlation between PABPN1 Genotype and Disease Severity in Oculopharyngeal Muscular Dystrophy"> Richard, Pascale, et al. “Correlation between PABPN1 Genotype and Disease Severity in Oculopharyngeal Muscular Dystrophy.” Neurology, vol. 88, no. 4, 2016, pp. 359–365., doi:10.1212/wnl.0000000000003554. </ref>	+	Oculopharyngeal muscular dystrophy, or [https://rarediseases.info.nih.gov/diseases/7245/oculopharyngeal-muscular-dystrophy OPMD], is an autosomal dominant late-onset disease. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> The disease is characterized by the myopathy of the eyelids and the throat with symptoms consisting of eye-drooping and difficulty swallowing. There are two types of OPMD: autosomal dominant and recessive, both originating from the mutation of the PABP nuclear 1 [https://en.wikipedia.org/wiki/PABPN1 (PABPN1)] gene located on the long arm of chromosome 14. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> This mutation results in an abnormally long polyalanine tract, 11-18 alanines, opposed to the normal 10. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> Patients with longer PABPN1 expansion (more alanines) are on average diagnosed at an earlier in life than patients with a shorter expansion; therefore, expansion size plays a role in OPMD severity and progression. <ref name="“Correlation between PABPN1 Genotype and Disease Severity in Oculopharyngeal Muscular Dystrophy"> Richard, Pascale, et al. “Correlation between PABPN1 Genotype and Disease Severity in Oculopharyngeal Muscular Dystrophy.” Neurology, vol. 88, no. 4, 2016, pp. 359–365., doi:10.1212/wnl.0000000000003554. </ref> This mutation results in PABPN1 forming clumps in muscle cells that can’t be degraded. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> It’s suspected that this is a source of cell death for effected cells, however, it has not been concluded why this mutation only affects certain muscle cells.
-		+
-	~~The~~ mutation results in PABPN1 forming clumps in muscle cells that can’t be degraded. <ref name="Oculopharyngeal Muscular Dystrophy">“Oculopharyngeal Muscular Dystrophy.” NORD (National Organization for Rare Disorders), rarediseases.org/rare-diseases/oculopharyngeal-muscular-dystrophy/.</ref> It’s suspected that this is a source of cell death for effected cells, however, it has not been concluded why this mutation only affects certain muscle cells.	+

	===Studies on Mutations===		===Studies on Mutations===

Ben Dawson at 21:01, 23 April 2018

2018-04-23T21:01:21Z

←Older revision		Revision as of 21:01, 23 April 2018
Line 63:		Line 63:
	Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.		Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.

-	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3).¹ Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> ~~[[Image:closedlooper.png\|300px\|left\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]]~~	+	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3).¹ Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> [[Image:closedlooper.png\|300px\|left\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]] The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>
-		+
-		+

	In more complex eukaryotic organisms, PABP indirectly stimulates translation via [https://en.wikipedia.org/wiki/PAIP1 PAIP-1] (PABP interacting protein). A higher presence of PAIP-1 increases the rate of translation initiation, indicating another way to “close the loop.”¹		In more complex eukaryotic organisms, PABP indirectly stimulates translation via [https://en.wikipedia.org/wiki/PAIP1 PAIP-1] (PABP interacting protein). A higher presence of PAIP-1 increases the rate of translation initiation, indicating another way to “close the loop.”¹

Ben Dawson at 21:00, 23 April 2018

2018-04-23T21:00:00Z

←Older revision		Revision as of 21:00, 23 April 2018
Line 63:		Line 63:
	Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.		Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.

-	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3).¹ Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> [[Image:closedlooper.png\|300px\|~~right~~\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]]	+	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3).¹ Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> [[Image:closedlooper.png\|300px\|left\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]]

Ben Dawson at 20:59, 23 April 2018

2018-04-23T20:59:22Z

←Older revision		Revision as of 20:59, 23 April 2018
Line 60:		Line 60:

	===Eukaryotic Translation Initiation===		===Eukaryotic Translation Initiation===
-	Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G. [[Image:~~Dorsal side~~.~~jpg~~\|~~200px~~\|right\|thumb\| "Figure 2:"~~Dorsal side with green conserved residues that interact with eIF4.~~]]	+	[[Image:Dorsal side.jpg\|200px\|right\|thumb\| "Figure 2:"Dorsal side with green conserved residues that interact with eIF4.]]
		+	Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (Figure2) (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.
		+
		+	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3).¹ Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> [[Image:closedlooper.png\|300px\|right\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]]

-	PABP and mRNA complex aids in translation initiation under two proposed mechanisms. Within the two mechanisms, studies have highlighted the presence The “Closed Loop” Model entails the recognition of the 5’ 7-methyl-Guanosine cap by [https://en.wikipedia.org/wiki/Eukaryotic_initiation_factor_4F eIF4F], which is a ternary complex made up of a cap-binding protein [https://en.wikipedia.org/wiki/EIF4E (eIF4E)] and RNA helicase [https://en.wikipedia.org/wiki/EIF4A (eIF4A)] connected by the bridging protein (eIF4G) (Figure 3).¹ Translation initiation is stimulated by the PABP bound to the poly(A) tail and its association with eIF4G.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The 5’ UTR is unwound by the elF4F complex, and ribosomes are recruited to create the initiation complex. The eIF4G protein then guides the 40S subunit to the start codon (AUG), which is followed by the binding 60S ribosomal subunit, creating the 80S initiation complex.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> The association of the PABP and eIF4G gave rise to the name “closed loop.”<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Mutations of Arg→Ala and Lys→Ala in human eIF4G and in yeast extracts decrease the rate of translation initiation and destabilizing the interactions with PABP, indicating that basic residues are essential to the interaction with PABP.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>

-	[[Image:closedlooper.png\|300px\|right\|thumb\| "Figure 3:" Closed loop model of the eIF4F complex and PABP creating a loop out of the mRNA ]]

	In more complex eukaryotic organisms, PABP indirectly stimulates translation via [https://en.wikipedia.org/wiki/PAIP1 PAIP-1] (PABP interacting protein). A higher presence of PAIP-1 increases the rate of translation initiation, indicating another way to “close the loop.”¹		In more complex eukaryotic organisms, PABP indirectly stimulates translation via [https://en.wikipedia.org/wiki/PAIP1 PAIP-1] (PABP interacting protein). A higher presence of PAIP-1 increases the rate of translation initiation, indicating another way to “close the loop.”¹

Ben Dawson at 20:58, 23 April 2018

2018-04-23T20:58:24Z

(Difference between revisions)

Ben Dawson at 20:12, 23 April 2018

2018-04-23T20:12:53Z

←Older revision		Revision as of 20:12, 23 April 2018
Line 9:		Line 9:

	== Structure ==		== Structure ==
-	<StructureSection load='1cvj' size='340' side='right' caption='PABP' scene='78/782614/Structure_scene_color_scheme/1'>	+	<StructureSection load='1cvj' size='340' side='right' caption='PABP' scene='78/782614/Structure_scene_color_scheme/1'> __NoTOC__
-	__NoTOC__	+
	The crystal structure PABP was derived from X-ray Diffraction at 2.6Å (R-value: 23%). The subunits of PABP, RRM1 and RRM2, are examined in this article as the ''in vivo'' form seen in biological assembly 1 (via PDB). The protein has a homopolymeric structure, containing four RNA recognition motifs (RRMs), which are conserved. <ref name="Structure and Function">Kühn, Uwe and Elmar, Wahle. “Structure and Function of Poly(a) Binding Proteins.” Bba - Gene Structure & Expression, vol. 1678, no. 2/3, 2004. </ref> <scene name='78/782616/Rrm1_only/2'>RRM1</scene> and <scene name='78/782616/Rrm2_only/2'>RRM2</scene> are N-terminal domains that are connected by a <scene name='78/782616/Linker/3'>linker</scene>.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Opposed to their counterparts, RRM3 and RRM4 bind Poly (A) RNA less tightly than RRM1 and RRM2.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>		The crystal structure PABP was derived from X-ray Diffraction at 2.6Å (R-value: 23%). The subunits of PABP, RRM1 and RRM2, are examined in this article as the ''in vivo'' form seen in biological assembly 1 (via PDB). The protein has a homopolymeric structure, containing four RNA recognition motifs (RRMs), which are conserved. <ref name="Structure and Function">Kühn, Uwe and Elmar, Wahle. “Structure and Function of Poly(a) Binding Proteins.” Bba - Gene Structure & Expression, vol. 1678, no. 2/3, 2004. </ref> <scene name='78/782616/Rrm1_only/2'>RRM1</scene> and <scene name='78/782616/Rrm2_only/2'>RRM2</scene> are N-terminal domains that are connected by a <scene name='78/782616/Linker/3'>linker</scene>.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Opposed to their counterparts, RRM3 and RRM4 bind Poly (A) RNA less tightly than RRM1 and RRM2.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>

Ben Dawson at 18:49, 20 April 2018

2018-04-20T18:49:48Z

←Older revision		Revision as of 18:49, 20 April 2018
Line 14:		Line 14:


-	~~'''~~RNA Recognition Motifs (RRMs)~~'''~~	+	===RNA Recognition Motifs (RRMs)===
	The <scene name='78/782616/Subunits_of_pabp/3'>Components of PABP</scene> are categorized into two RRMs: the n-terminus RRM1 (red) and c-terminus RRM2 (blue) are shown accordingly. The two RRMs are linked via an alpha-helix linker (green) that maintains the RRM1/2 complex that is the biological assembly and active form of PABP. Each RRM has a four-stranded antiparallel beta sheet backed by two corresponding alpha helices. <ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> mRNA poly-adenosine recognition is due to the presence of the conserved residues within the beta-sheet surface <ref name="The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.">Wang, Zuoren and Kiledjian, Megerditch. “The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.” Molecular and Cellular Biology 20.17 (2000): 6334–6341. Print.</ref> , which forms a <scene name='78/782616/Trough2/1'>trough</scene>-like pocket for the mRNA to bind. The beta-sheet flooring present in PABP interacts with the 3’ mRNA tail via combination of van der Waals, aromatic stacking, and Hydrogen bonding. Through these interactions, PABP binds to 3’ Poly (A) tail with a KD of 2-7 nM. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref> [[Image:Hydrophobicity (1).png\|200px\|right\|thumb\| "Figure 1:" Surface hydrophobicity shown in presence of mRNA]]		The <scene name='78/782616/Subunits_of_pabp/3'>Components of PABP</scene> are categorized into two RRMs: the n-terminus RRM1 (red) and c-terminus RRM2 (blue) are shown accordingly. The two RRMs are linked via an alpha-helix linker (green) that maintains the RRM1/2 complex that is the biological assembly and active form of PABP. Each RRM has a four-stranded antiparallel beta sheet backed by two corresponding alpha helices. <ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> mRNA poly-adenosine recognition is due to the presence of the conserved residues within the beta-sheet surface <ref name="The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.">Wang, Zuoren and Kiledjian, Megerditch. “The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.” Molecular and Cellular Biology 20.17 (2000): 6334–6341. Print.</ref> , which forms a <scene name='78/782616/Trough2/1'>trough</scene>-like pocket for the mRNA to bind. The beta-sheet flooring present in PABP interacts with the 3’ mRNA tail via combination of van der Waals, aromatic stacking, and Hydrogen bonding. Through these interactions, PABP binds to 3’ Poly (A) tail with a KD of 2-7 nM. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref> [[Image:Hydrophobicity (1).png\|200px\|right\|thumb\| "Figure 1:" Surface hydrophobicity shown in presence of mRNA]]

Line 21:		Line 21:


-	===Interactions===	+	==Interactions==

	'''Adenosine Recognition Interactions'''		'''Adenosine Recognition Interactions'''
Line 41:		Line 41:


-	~~'''~~mRNA Stabilization via Aromatic Stacking~~'''~~	+	===mRNA Stabilization via Aromatic Stacking===
	<table><tr><td colspan='2'>		<table><tr><td colspan='2'>
	<tr id='Adenosine Number'><td class="sblockLbl"><b>Adenosine Number</b></td><td class="sblockDat">PABP residue</td><tr>		<tr id='Adenosine Number'><td class="sblockLbl"><b>Adenosine Number</b></td><td class="sblockDat">PABP residue</td><tr>
Line 50:		Line 50:


-	=== Function ===	+	== Function ==
	In eukaryotic mRNA translation, PABP recognizes the 3' Poly(A) tail via trough interactions determined above. While associated with the Poly(A) region, the complex then works together to stabilize the mRNA by preventing exoribonucleolytic degradation,<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> thereby guiding the mRNA molecule into the translation pathway via interactions with translation initiation factor gG.		In eukaryotic mRNA translation, PABP recognizes the 3' Poly(A) tail via trough interactions determined above. While associated with the Poly(A) region, the complex then works together to stabilize the mRNA by preventing exoribonucleolytic degradation,<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> thereby guiding the mRNA molecule into the translation pathway via interactions with translation initiation factor gG.


-	~~'''~~Recognition of the Poly(A) Tail~~'''~~	+	===Recognition of the Poly(A) Tail===

	Polyadenylation of an mRNA involves the recognition of the 5’-AAUAAA-3’ consensus site, the cleavage downstream of the consensus site, and then the addition of adenines by [https://en.wikipedia.org/wiki/Polynucleotide_adenylyltransferase Poly(A) Polymerase] to the 3’ end. The newly added poly(A) tail is associated with the PABP. PABP requires 11-12 adenosines in order to bind. PABP and the bound Poly(A) tail work together to stabilize mRNA by preventing exo-ribonucleolytic degradation,<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> thereby guiding the mRNA molecule into the translation pathway. Upon mRNA poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor [https://en.wikipedia.org/wiki/EIF4G eIF4G].		Polyadenylation of an mRNA involves the recognition of the 5’-AAUAAA-3’ consensus site, the cleavage downstream of the consensus site, and then the addition of adenines by [https://en.wikipedia.org/wiki/Polynucleotide_adenylyltransferase Poly(A) Polymerase] to the 3’ end. The newly added poly(A) tail is associated with the PABP. PABP requires 11-12 adenosines in order to bind. PABP and the bound Poly(A) tail work together to stabilize mRNA by preventing exo-ribonucleolytic degradation,<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> thereby guiding the mRNA molecule into the translation pathway. Upon mRNA poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor [https://en.wikipedia.org/wiki/EIF4G eIF4G].


-	~~'''~~mRNA Stabilization~~'''~~	+	===mRNA Stabilization===

	PABP prevents the deadenylation and decapping of the mRNA, serving as a source of stabilization. Poly(A) ribonuclease [https://en.wikipedia.org/wiki/Poly(A)-specific_ribonuclease (PARN)] work to deadenylate mRNA, but the presence of PABP prevents its activity. The PABP protein is able to protect mRNA degradation through the complex that it forms with the elongation initiation factors, which prevent deadenylation and decapping due to their presence.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> This has been verified by the presence of deadenylation products and the comparative size of PABP footprints. There is some evidence indicating that PABP is involved in the prevention of endonucleolytic cleavage; however, only a small amount of mRNA is degraded from endonucleolytic cleavage, so it is not widely researched.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>		PABP prevents the deadenylation and decapping of the mRNA, serving as a source of stabilization. Poly(A) ribonuclease [https://en.wikipedia.org/wiki/Poly(A)-specific_ribonuclease (PARN)] work to deadenylate mRNA, but the presence of PABP prevents its activity. The PABP protein is able to protect mRNA degradation through the complex that it forms with the elongation initiation factors, which prevent deadenylation and decapping due to their presence.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> This has been verified by the presence of deadenylation products and the comparative size of PABP footprints. There is some evidence indicating that PABP is involved in the prevention of endonucleolytic cleavage; however, only a small amount of mRNA is degraded from endonucleolytic cleavage, so it is not widely researched.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>


-	~~'''~~Eukaryotic Translation Initiation~~'''~~	+	===Eukaryotic Translation Initiation===

	Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.		Upon mRNA Poly(A) recognition, PABP and the bound mRNA stimulate the initiation of translation by interacting with initiation factor eIF4G. Protein eIF4G actually interacts with PABP's dorsal side (under the trough) hydrophobic and acidic residues that stimulate the interaction between the two proteins. These specific residues are phylogenetically conserved among all PABPs, and therefore significant in the protein's function and interaction with eIF4G.

Ben Dawson at 18:48, 20 April 2018

2018-04-20T18:48:44Z

←Older revision		Revision as of 18:48, 20 April 2018
Line 8:		Line 8:


-	== Structure~~, Interactions, Function~~ ==	+	== Structure ==
	<StructureSection load='1cvj' size='340' side='right' caption='PABP' scene='78/782614/Structure_scene_color_scheme/1'>		<StructureSection load='1cvj' size='340' side='right' caption='PABP' scene='78/782614/Structure_scene_color_scheme/1'>
		+	__NoTOC__
	The crystal structure PABP was derived from X-ray Diffraction at 2.6Å (R-value: 23%). The subunits of PABP, RRM1 and RRM2, are examined in this article as the ''in vivo'' form seen in biological assembly 1 (via PDB). The protein has a homopolymeric structure, containing four RNA recognition motifs (RRMs), which are conserved. <ref name="Structure and Function">Kühn, Uwe and Elmar, Wahle. “Structure and Function of Poly(a) Binding Proteins.” Bba - Gene Structure & Expression, vol. 1678, no. 2/3, 2004. </ref> <scene name='78/782616/Rrm1_only/2'>RRM1</scene> and <scene name='78/782616/Rrm2_only/2'>RRM2</scene> are N-terminal domains that are connected by a <scene name='78/782616/Linker/3'>linker</scene>.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Opposed to their counterparts, RRM3 and RRM4 bind Poly (A) RNA less tightly than RRM1 and RRM2.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>		The crystal structure PABP was derived from X-ray Diffraction at 2.6Å (R-value: 23%). The subunits of PABP, RRM1 and RRM2, are examined in this article as the ''in vivo'' form seen in biological assembly 1 (via PDB). The protein has a homopolymeric structure, containing four RNA recognition motifs (RRMs), which are conserved. <ref name="Structure and Function">Kühn, Uwe and Elmar, Wahle. “Structure and Function of Poly(a) Binding Proteins.” Bba - Gene Structure & Expression, vol. 1678, no. 2/3, 2004. </ref> <scene name='78/782616/Rrm1_only/2'>RRM1</scene> and <scene name='78/782616/Rrm2_only/2'>RRM2</scene> are N-terminal domains that are connected by a <scene name='78/782616/Linker/3'>linker</scene>.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Opposed to their counterparts, RRM3 and RRM4 bind Poly (A) RNA less tightly than RRM1 and RRM2.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>

Ben Dawson at 18:46, 20 April 2018

2018-04-20T18:46:39Z

←Older revision		Revision as of 18:46, 20 April 2018
Line 14:		Line 14:

	'''RNA Recognition Motifs (RRMs)'''		'''RNA Recognition Motifs (RRMs)'''
-	The <scene name='78/782616/Subunits_of_pabp/3'>Components of PABP</scene> are categorized into two RRMs: the n-terminus RRM1 (red) and c-terminus RRM2 (blue) are shown accordingly. The two RRMs are linked via an alpha-helix linker (green) that maintains the RRM1/2 complex that is the biological assembly and active form of PABP. Each RRM has a four-stranded antiparallel beta sheet backed by two corresponding alpha helices. <ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> mRNA poly-adenosine recognition is due to the presence of the conserved residues within the beta-sheet surface <ref name="The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.">Wang, Zuoren and Kiledjian, Megerditch. “The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.” Molecular and Cellular Biology 20.17 (2000): 6334–6341. Print.</ref> , which forms a <scene name='78/782616/Trough2/1'>trough</scene>-like pocket for the mRNA to bind. The beta-sheet flooring present in PABP interacts with the 3’ mRNA tail via a combination of van der Waals, aromatic stacking, and Hydrogen bonding. Through these interactions, PABP binds to 3’ Poly (A) tail with a KD of 2-7 nM. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref> [[Image:Hydrophobicity (1).png\|200px\|right\|thumb\| "Figure 1:" Surface hydrophobicity shown in presence of mRNA]]	+	The <scene name='78/782616/Subunits_of_pabp/3'>Components of PABP</scene> are categorized into two RRMs: the n-terminus RRM1 (red) and c-terminus RRM2 (blue) are shown accordingly. The two RRMs are linked via an alpha-helix linker (green) that maintains the RRM1/2 complex that is the biological assembly and active form of PABP. Each RRM has a four-stranded antiparallel beta sheet backed by two corresponding alpha helices. <ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> mRNA poly-adenosine recognition is due to the presence of the conserved residues within the beta-sheet surface <ref name="The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.">Wang, Zuoren and Kiledjian, Megerditch. “The Poly(A)-Binding Protein and an mRNA Stability Protein Jointly Regulate an Endoribonuclease Activity.” Molecular and Cellular Biology 20.17 (2000): 6334–6341. Print.</ref> , which forms a <scene name='78/782616/Trough2/1'>trough</scene>-like pocket for the mRNA to bind. The beta-sheet flooring present in PABP interacts with the 3’ mRNA tail via combination of van der Waals, aromatic stacking, and Hydrogen bonding. Through these interactions, PABP binds to 3’ Poly (A) tail with a KD of 2-7 nM. <ref name="Roles of Cytoplasmic Poly(A)-Binding Proteins">Gorgoni, Barbra, and Gray, Nicola. “The Roles of Cytoplasmic Poly(A)-Binding Proteins in Regulating Gene Expression: A Developmental Perspective.” Briefings in Functional Genomics and Proteomics, vol. 3, no. 2, 1 Aug. 2004, pp. 125–141., doi:10.1093/bfgp/3.2.125.</ref> [[Image:Hydrophobicity (1).png\|200px\|right\|thumb\| "Figure 1:" Surface hydrophobicity shown in presence of mRNA]]

Ben Dawson at 18:41, 20 April 2018

2018-04-20T18:41:34Z

←Older revision		Revision as of 18:41, 20 April 2018
Line 8:		Line 8:


-	== Structure, Interactions, & Function ==	+	== Structure, Interactions, Function ==
	<StructureSection load='1cvj' size='340' side='right' caption='PABP' scene='78/782614/Structure_scene_color_scheme/1'>		<StructureSection load='1cvj' size='340' side='right' caption='PABP' scene='78/782614/Structure_scene_color_scheme/1'>
	The crystal structure PABP was derived from X-ray Diffraction at 2.6Å (R-value: 23%). The subunits of PABP, RRM1 and RRM2, are examined in this article as the ''in vivo'' form seen in biological assembly 1 (via PDB). The protein has a homopolymeric structure, containing four RNA recognition motifs (RRMs), which are conserved. <ref name="Structure and Function">Kühn, Uwe and Elmar, Wahle. “Structure and Function of Poly(a) Binding Proteins.” Bba - Gene Structure & Expression, vol. 1678, no. 2/3, 2004. </ref> <scene name='78/782616/Rrm1_only/2'>RRM1</scene> and <scene name='78/782616/Rrm2_only/2'>RRM2</scene> are N-terminal domains that are connected by a <scene name='78/782616/Linker/3'>linker</scene>.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Opposed to their counterparts, RRM3 and RRM4 bind Poly (A) RNA less tightly than RRM1 and RRM2.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>		The crystal structure PABP was derived from X-ray Diffraction at 2.6Å (R-value: 23%). The subunits of PABP, RRM1 and RRM2, are examined in this article as the ''in vivo'' form seen in biological assembly 1 (via PDB). The protein has a homopolymeric structure, containing four RNA recognition motifs (RRMs), which are conserved. <ref name="Structure and Function">Kühn, Uwe and Elmar, Wahle. “Structure and Function of Poly(a) Binding Proteins.” Bba - Gene Structure & Expression, vol. 1678, no. 2/3, 2004. </ref> <scene name='78/782616/Rrm1_only/2'>RRM1</scene> and <scene name='78/782616/Rrm2_only/2'>RRM2</scene> are N-terminal domains that are connected by a <scene name='78/782616/Linker/3'>linker</scene>.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref> Opposed to their counterparts, RRM3 and RRM4 bind Poly (A) RNA less tightly than RRM1 and RRM2.<ref name="Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein">Deo, Rahul C, et al. “Recognition of Polyadenylate RNA by the Poly(A)-Binding Protein.” Cell 98:6. (1999) 835-845. Print. </ref>