RNA polymerase motions during promoter melting

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Science  26 May 2017:
Vol. 356, Issue 6340, pp. 863-866
DOI: 10.1126/science.aam7858

Trapping RNA polymerase in the act

The enzyme RNA polymerase (RNAP) finds promoter elements in the genome, separates (or “melts”) the DNA strands, and transcribes the template DNA strand to give RNA. A mobile clamp in RNAP plays a key role in initiating transcription. Feklistov et al. locked the clamp of bacterial RNAP in distinct conformations by using small molecules. They then used fluorescent probes to monitor binding as the promoter DNA was separated. Unexpectedly, they found that the clamp transiently closed to nucleate DNA melting, opened to load single-stranded DNA into the active site, and then closed around the template strand to start transcription.

Science, this issue p. 863