6cnb

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Yeast RNA polymerase III initial transcribing complex

6cnb, resolution 4.10Å

Structural highlights

6cnb is a 10 chain structure with sequence from Saccharomyces cerevisiae S288C. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	Electron Microscopy, Resolution 4.1Å
Ligands:
Experimental data:	Check to display Experimental Data
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

RPC1_YEAST DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Largest and catalytic core component of RNA polymerase III which synthesizes small RNAs, such as 5S rRNA and tRNAs. Forms the polymerase active center together with the second largest subunit. A single-stranded DNA template strand of the promoter is positioned within the central active site cleft of Pol III. A bridging helix emanates from RPC1 and crosses the cleft near the catalytic site and is thought to promote translocation of Pol III 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 (By similarity).

Publication Abstract from PubMed

RNA polymerase III (Pol III) transcription initiation requires the action of the transcription factor IIIB (TFIIIB) and is highly regulated. Here, we determine the structures of Pol III pre-initiation complexes (PICs) using single particle cryo-electron microscopy (cryo-EM). We observe stable Pol III-TFIIIB complexes using nucleic acid scaffolds mimicking various functional states, in which TFIIIB tightly encircles the upstream promoter DNA. There is an intricate interaction between TFIIIB and Pol III, which stabilizes the winged-helix domains of the C34 subunit of Pol III over the active site cleft. The architecture of Pol III PIC more resembles that of the Pol II PIC than the Pol I PIC. In addition, we also obtain a 3D reconstruction of Pol III in complex with TFIIIB using the elongation complex (EC) scaffold, shedding light on the mechanism of facilitated recycling of Pol III prior to transcription re-initiation.

Structural visualization of RNA polymerase III transcription machineries.,Han Y, Yan C, Fishbain S, Ivanov I, He Y Cell Discov. 2018 Jul 31;4:40. doi: 10.1038/s41421-018-0044-z. eCollection 2018. PMID:30083386^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Han Y, Yan C, Fishbain S, Ivanov I, He Y. Structural visualization of RNA polymerase III transcription machineries. Cell Discov. 2018 Jul 31;4:40. doi: 10.1038/s41421-018-0044-z. eCollection 2018. PMID:30083386 doi:http://dx.doi.org/10.1038/s41421-018-0044-z