Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase

Article (PDF Available)inJournal of Visualized Experiments 327(38) · January 2010with14 Reads
DOI: 10.3791/1919 · Source: PubMed
Abstract
In vivo studies suggest that replication forks are arrested by encounters with head-on transcription complexes. Yet, the fate of the replisome and RNA polymerase (RNAP) after a head-on collision is unknown. We found that the Escherichia coli replisome stalls upon collision with a head-on transcription complex, but instead of collapsing, the replication fork remains highly stable and eventually resumes elongation after displacing the RNAP from DNA. We also found that the transcription-repair coupling factor Mfd promotes direct restart of the fork after the collision by facilitating displacement of the RNAP. These findings demonstrate the intrinsic stability of the replication apparatus and a previously unknown role for the transcription-coupled repair pathway in promoting replication past a RNAP block.

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    • "Two types of collisions are possible; head to head or co-directional. Head to head collisions appear to be more detrimental to cell viability686970 since ribosomal operons and other highly transcribed genes are encoded on the leading DNA strand, and therefore transcribed codirectionally with replication fork progression [71]. However, codirectional collisions are still inevitable because the DNA polymerase moves at least 10 times faster than RNAP [72]. "
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