Nucleic Acids Research Advance Access originally published online on August 21, 2007
Nucleic Acids Research 2007 35(17):5694-5705; doi:10.1093/nar/gkm600
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Nucleic Acids Research, 2007, Vol. 35, No. 17 5694-5705
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
Allosteric control of the RNA polymerase by the elongation factor RfaH
1Department of Microbiology, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210 and 2Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 720 20th Street South, Birmingham, AL 35294, USA
*To whom correspondence should be addressed. Tel: 614 292 6777; Fax: 614 292 8120; Email: artsimovitch.1{at}osu.edu
Received May 31, 2007. Revised July 17, 2007. Accepted July 23, 2007.
Efficient transcription of long polycistronic operons in bacteria frequently relies on accessory proteins but their molecular mechanisms remain obscure. RfaH is a cellular elongation factor that acts as a polarity suppressor by increasing RNA polymerase (RNAP) processivity. In this work, we provide evidence that RfaH acts by reducing transcriptional pausing at certain positions rather than by accelerating RNAP at all sites. We show that ‘fast’ RNAP variants are characterized by pause-free RNA chain elongation and are resistant to RfaH action. Similarly, the wild-type RNAP is insensitive to RfaH in the absence of pauses. In contrast, those enzymes that may be prone to falling into a paused state are hypersensitive to RfaH. RfaH inhibits pyrophosphorolysis of the nascent RNA and reduces the apparent Michaelis–Menten constant for nucleotides, suggesting that it stabilizes the post-translocated, active RNAP state. Given that the RfaH-binding site is located 75 Å away from the RNAP catalytic center, these results strongly indicate that RfaH acts allosterically. We argue that despite the apparent differences in the nucleic acid targets, the time of recruitment and the binding sites on RNAP, unrelated antiterminators (such as RfaH and 
Q) utilize common strategies during both recruitment and anti-pausing modification of the transcription complex.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.
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  A. Sevostyanova, V. Svetlov, D. G. Vassylyev, and I. Artsimovitch The elongation factor RfaH and the initiation factor {sigma} bind to the same site on the transcription elongation complex PNAS, January 22, 2008; 105(3): 865 - 870. [Abstract] [Full Text] [PDF]
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