RNA polymerase 2 largest subunit; RPB1; RNA polymerase 2 subunit A; RNA polymerase 2 subunit B1 (POLR2A)
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Function
- largest & catalytic component of RNA polymerase 2
- forms the polymerase active center together with the 2nd largest subunit (POLR2B)
- POLR2A is part of the core element with the central large cleft, the clamp element that moves to open & close the cleft & the jaws that are thought to grab the incoming DNA template
- a bridging helix emanates from POLR2A & crosses the cleft near the catalytic site & is thought to promote translocation of RNA polymerase 2 by acting as a ratchet that moves the RNA-DNA hybrid through the active site by switching from straight to bent conformations at each step of nucleotide addition
- binding of ribonucleoside triphosphate to the RNA polymerase 2 transcribing complex probably involves a two- step mechanism
- initial binding seems to occur at the entry (E) site & involves a Mg+2 temporarily coordinated by 3 conserved Asp of the two largest RNA polymerase 2 subunits (POLR2A & POLR2B)
- the ribonucleoside triphosphate is transferred by a rotation to the nucelotide addition (A) site for pairing with the template DNA
- the catalytic A site involves 3 conserved Asp of POLR2A permanently coordinating a 2nd Mg+2
- elongation is influenced by the phosphorylation status of the C-terminal domain (CTD) of POLR2A, which serves as a platform for assembly of factors that regulate transcription initiation, elongation, termination & mRNA processing
- phosphorylated C-terminal domain interacts with FNBP3 & SYNCRIP
- interacts with SAFB/SAFB1
- interacts with CCNL1 (putative)
- interacts with CCNL2 & SFRS19
- component of a complex which is at least composed of HTATSF1/Tat-SF1, the P-TEFb complex components CDK9 & CCNT1, RNA polymerase 2, SUPT5H, & NCL/nucleolin
- tandem 7 residues repeats in the C-terminal domain (CTD) can be highly phosphorylated
- phosphorylation activates RNA polymerase 2
- occurs mainly at residues Ser-2 & Ser-5 of the heptapepdtide repeat
- phosphorylation state is believed to result from the balanced action of site-specific CTD kinases & phosphoprotein phosphatases, & a CTD code that specifies the position of RNA polymerase 2 within the transcription cycle
Structure
- belongs to the RNA polymerase beta' chain family
- contains 1 C2H2-type Zn+2 finger
Compartment
More general terms
Component of
References
- ↑ Molecular Cell Biology (2nd ed) Darnell J; Lodish H & Baltimore D (eds), Scientific American Books, WH Freeman, NY 1990, pg 266
- ↑ UniProt http://www.uniprot.org/uniprot/P24928.html