Prp8
From Proteopedia
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==Pre-mRNA Splicing== | ==Pre-mRNA Splicing== | ||
| - | Splicing is an essential process in the cell is because immediately following transcription, the pre-mRNA contains both intronic and exonic sequences. The exonic sequences are the protein coding portions of the RNA which contain codons that directly specify which amino acids will be incorporated into a newly synthesized protein. Conversely, the intronic sequences are non-coding portions of the pre-mRNA which need to be removed in order to form an uninterrupted coding sequence known as mature-mRNA. | ||
Pre-mRNA splicing is carried out by one of the most complex pieces of cellular machinery known to date; the Spliceosome. It is a large, catalytic protein-RNA complex responsible for removing the intronic sequences of pre-mRNA and “splicing” together the exonic sequences to form mature mRNA. The spliceosome is made up of approximately 145 distinct spliceosomal proteins, and five small nuclear RNAs (snRNAs) <ref name='Comprehensive proteomic analysis of the human spliceosome'>DOI:10.1038/nature01031</ref>. The five snRNAs have been subsequently named U1, U2, U4, U5, and U6. The spliceosome carries out a two-step transesterification reaction through a series of chemical steps in order to remove the intronic sequences from the pre-mRNA, which is facilitated by the movements, rearrangements, and dynamic exchanges of the snRNAs and splicing associated proteins <ref name='Messenger RNA Splicing in Yeast: Clues to Why the Spliceosome is a Ribonucleoprotein'>PMID:1853200</ref>. | Pre-mRNA splicing is carried out by one of the most complex pieces of cellular machinery known to date; the Spliceosome. It is a large, catalytic protein-RNA complex responsible for removing the intronic sequences of pre-mRNA and “splicing” together the exonic sequences to form mature mRNA. The spliceosome is made up of approximately 145 distinct spliceosomal proteins, and five small nuclear RNAs (snRNAs) <ref name='Comprehensive proteomic analysis of the human spliceosome'>DOI:10.1038/nature01031</ref>. The five snRNAs have been subsequently named U1, U2, U4, U5, and U6. The spliceosome carries out a two-step transesterification reaction through a series of chemical steps in order to remove the intronic sequences from the pre-mRNA, which is facilitated by the movements, rearrangements, and dynamic exchanges of the snRNAs and splicing associated proteins <ref name='Messenger RNA Splicing in Yeast: Clues to Why the Spliceosome is a Ribonucleoprotein'>PMID:1853200</ref>. | ||
Revision as of 21:36, 21 July 2012
Contents |
Introduction
Prp8 Background
Pre-mRNA Splicing
Pre-mRNA splicing is carried out by one of the most complex pieces of cellular machinery known to date; the Spliceosome. It is a large, catalytic protein-RNA complex responsible for removing the intronic sequences of pre-mRNA and “splicing” together the exonic sequences to form mature mRNA. The spliceosome is made up of approximately 145 distinct spliceosomal proteins, and five small nuclear RNAs (snRNAs) [1]. The five snRNAs have been subsequently named U1, U2, U4, U5, and U6. The spliceosome carries out a two-step transesterification reaction through a series of chemical steps in order to remove the intronic sequences from the pre-mRNA, which is facilitated by the movements, rearrangements, and dynamic exchanges of the snRNAs and splicing associated proteins [2].
First, the U1 snRNP recognizes and binds to the 5’ splice site of the pre-mRNA and the U2 snRNP recognizes and binds to the branch site of the intronic sequence, which contains a conserved adenine nucleotide, which is collectively known as complex A [3]. Subsequently, the U4/U6 U5 tri-snRNP moves in and associates with the intronic sequence (now known as complex B)[3]. This causes the U4 and U1 snRNPs to be displaced, forming the catalytically active spliceosome (complex B*) and the remaining U2, U5, and U6 snRNP facilitate the two transesterification reactions, dissociate from the now mature mRNA, and are recycled for subsequent use in another splicing reaction [3].
As stated above, the chemical mechanism pre-mRNA splicing follows is a two-step transesterification reaction. With the release of U1 and U4, following the subsequent rearrangement of the remaining snRNPs, the 2’ hydroxyl of the conserved adenine nucleotide carries out a nucleophilic attack on the 5’ splice site, which cuts the backbone of the mRNA, freeing the first exon [2]. Now the 5’ end of the intron is covalently bonded to the adenine nucleotide, forming a lariat structure [2]. Finally, the 3’ OH of the first exon nucleophilically attacks the 5’ end of the second exon, displacing the intron and splicing the exons together [2]. This is followed by the subsequent release of the lariat structure and the remaining spliceosome dissociates [2].
Structure of Prp8
Function of Prp8
Evolution of Prp8
References
- ↑ Zhou Z, Licklider LJ, Gygi SP, Reed R. Comprehensive proteomic analysis of the human spliceosome. Nature. 2002 Sep 12;419(6903):182-5. PMID:12226669 doi:10.1038/nature01031
- ↑ 2.0 2.1 2.2 2.3 2.4 Guthrie C. Messenger RNA splicing in yeast: clues to why the spliceosome is a ribonucleoprotein. Science. 1991 Jul 12;253(5016):157-63. PMID:1853200
- ↑ 3.0 3.1 3.2 Green MR. Biochemical mechanisms of constitutive and regulated pre-mRNA splicing. Annu Rev Cell Biol. 1991;7:559-99. PMID:1839712 doi:http://dx.doi.org/10.1146/annurev.cb.07.110191.003015
