7uif
Mediator-PIC Early (Core B)
Structural highlights
FunctionRPB3_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. RPB3 is part of the core element with the central large cleft and the clamp element that moves to open and close the cleft. Seems to be involved in transcription termination. Publication Abstract from PubMedMost eukaryotic promoter regions are divergently transcribed. As the RNA polymerase II pre-initiation complex (PIC) is intrinsically asymmetric and responsible for transcription in a single direction, it is unknown how divergent transcription arises. Here, the Saccharomyces cerevisiae Mediator complexed with a PIC (Med-PIC) was assembled on a divergent promoter and analyzed by cryoelectron microscopy. The structure reveals two distinct Med-PICs forming a dimer through the Mediator tail module, induced by a homodimeric activator protein localized near the dimerization interface. The tail dimer is associated with approximately 80-bp upstream DNA, such that two flanking core promoter regions are positioned and oriented in a suitable form for PIC assembly in opposite directions. Also, cryoelectron tomography visualized the progress of the PIC assembly on the two core promoter regions, providing direct evidence for the role of the Med-PIC dimer in divergent transcription. Structural basis of a transcription pre-initiation complex on a divergent promoter.,Gorbea Colon JJ, Palao L 3rd, Chen SF, Kim HJ, Snyder L, Chang YW, Tsai KL, Murakami K Mol Cell. 2023 Jan 26:S1097-2765(23)00031-X. doi: 10.1016/j.molcel.2023.01.011. PMID:36731470[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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