Send to

Choose Destination
Nature. 2007 Apr 12;446(7137):820-3. Epub 2007 Mar 14.

Backtracking determines the force sensitivity of RNAP II in a factor-dependent manner.

Author information

Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.


RNA polymerase II (RNAP II) is responsible for transcribing all messenger RNAs in eukaryotic cells during a highly regulated process that is conserved from yeast to human, and that serves as a central control point for cellular function. Here we investigate the transcription dynamics of single RNAP II molecules from Saccharomyces cerevisiae against force and in the presence and absence of TFIIS, a transcription elongation factor known to increase transcription through nucleosomal barriers. Using a single-molecule dual-trap optical-tweezers assay combined with a novel method to enrich for active complexes, we found that the response of RNAP II to a hindering force is entirely determined by enzyme backtracking. Surprisingly, RNAP II molecules ceased to transcribe and were unable to recover from backtracks at a force of 7.5 +/- 2 pN, only one-third of the force determined for Escherichia coli RNAP. We show that backtrack pause durations follow a t(-3/2) power law, implying that during backtracking RNAP II diffuses in discrete base-pair steps, and indicating that backtracks may account for most of RNAP II pauses. Significantly, addition of TFIIS rescued backtracked enzymes and allowed transcription to proceed up to a force of 16.9 +/- 3.4 pN. Taken together, these results describe a regulatory mechanism of transcription elongation in eukaryotes by which transcription factors modify the mechanical performance of RNAP II, allowing it to operate against higher loads.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Nature Publishing Group
Loading ...
Support Center