3j0k
From Proteopedia
Orientation of RNA polymerase II within the human VP16-Mediator-pol II-TFIIF assembly
Structural highlights
FunctionRPB7_YEAST DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Component of RNA polymerase II which synthesizes mRNA precursors and many functional non-coding RNAs. Pol II is the central component of the basal RNA polymerase II transcription machinery. It is composed of mobile elements that move relative to each other. RPB7 is part of a subcomplex with RPB4 that binds to a pocket formed by RPB1, RPB2 and RPB6 at the base of the clamp element. The RBP4-RPB7 subcomplex seems to lock the clamp via RPB7 in the closed conformation thus preventing double stranded DNA to enter the active site cleft. The RPB4-RPB7 subcomplex binds single-stranded DNA and RNA. The RPB4-RPB7 subcomplex recruits FCP1 to Pol II.[1] [2] [3] Publication Abstract from PubMedThe macromolecular assembly required to initiate transcription of protein-coding genes, known as the Pre-Initiation Complex (PIC), consists of multiple protein complexes and is approximately 3.5 MDa in size. At the heart of this assembly is the Mediator complex, which helps regulate PIC activity and interacts with the RNA polymerase II (pol II) enzyme. The structure of the human Mediator-pol II interface is not well-characterized, whereas attempts to structurally define the Mediator-pol II interaction in yeast have relied on incomplete assemblies of Mediator and/or pol II and have yielded inconsistent interpretations. We have assembled the complete, 1.9 MDa human Mediator-pol II-TFIIF complex from purified components and have characterized its structural organization using cryo-electron microscopy and single-particle reconstruction techniques. The orientation of pol II within this assembly was determined by crystal structure docking and further validated with projection matching experiments, allowing the structural organization of the entire human PIC to be envisioned. Significantly, pol II orientation within the Mediator-pol II-TFIIF assembly can be reconciled with past studies that determined the location of other PIC components relative to pol II itself. Pol II surfaces required for interacting with TFIIB, TFIIE, and promoter DNA (i.e., the pol II cleft) are exposed within the Mediator-pol II-TFIIF structure; RNA exit is unhindered along the RPB4/7 subunits; upstream and downstream DNA is accessible for binding additional factors; and no major structural re-organization is necessary to accommodate the large, multi-subunit TFIIH or TFIID complexes. The data also reveal how pol II binding excludes Mediator-CDK8 subcomplex interactions and provide a structural basis for Mediator-dependent control of PIC assembly and function. Finally, parallel structural analysis of Mediator-pol II complexes lacking TFIIF reveal that TFIIF plays a key role in stabilizing pol II orientation within the assembly. Molecular architecture of the human Mediator-RNA polymerase II-TFIIF assembly.,Bernecky C, Grob P, Ebmeier CC, Nogales E, Taatjes DJ PLoS Biol. 2011 Mar;9(3):e1000603. Epub 2011 Mar 29. PMID:21468301[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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