Sandbox Reserved 1275
From Proteopedia
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<scene name='75/751168/Rna_pol_ii_hydrophobic_regions/1'>Hydrophobic Regions</scene> | <scene name='75/751168/Rna_pol_ii_hydrophobic_regions/1'>Hydrophobic Regions</scene> | ||
<scene name='75/751168/Rna_pol_ii_helix/1'>Helix</scene> | <scene name='75/751168/Rna_pol_ii_helix/1'>Helix</scene> | ||
Revision as of 21:16, 8 February 2017
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RNA Polymerase II is the main workhorse of transcription, and is present in all eukaryotes. It is responsible for transcribing pre-mRNA, some snRNAs, snorRNAs, and some miRNAs. RNA Pol II participates in the initiation, elongation, and termination of transcription. RNA Pol II and several transcription factors form the basal transcription apparatus, which attaches to the core promoter and initiates conformational changes in the DNA. Then the template strand of DNA binds to the active site of RNA Pol II and forms an open complex. This complex is where two phosphate groups are cleaved off the nucleoside triphosphates and the nucleotides join together to make an RNA molecule.
The structure of RNA Pol II itself consists of a wall of amino acids, a pore, a funnel, and a groove. The DNA double helix enters through the groove and unwinds. Due to the angle between the exit and entry points of RNA Pol II, the DNA-RNA hybrid bends and the 3' end of RNA is positioned at the enzyme's active site; thus, new nucleotides can be added to this 3' end.
RNA Pol II does not have a specific termination sequence. Instead, it continues synthesizing RNA past the necessary point. This then requires the exonuclease enzyme Rat1 to degrade the extra nucleotides synthesized by RNA Pol II, after it has been cleaved from the pre-mRNA. Once Rat1 reaches the polymerase, both enzymes detach from the DNA and transcription ends.
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