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EMBO reports 8, 11, 1038–1043 (2007)
doi:10.1038/sj.embor.7401079
AOP Published online: 5 October 2007
The carboxy-terminal coiled-coil of the RNA polymerase  '-subunit is the main binding site for Gre factors
Marina N Vassylyeva1*, Vladimir Svetlov2*, Altaira D Dearborn1, Sergiy Klyuyev1, Irina Artsimovitch2 & Dmitry G Vassylyev1
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1 Department of Biochemistry and Molecular Genetics, Schools of Medicine and Dentistry, University of Alabama at Birmingham, 402B Kaul Genetics Building, 720 20th Street South, Birmingham, Alabama 35294, USA
2 Department of Microbiology, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio 43210, USA
To whom correspondence should be addressed
Irina Artsimovitch Tel: +1 614 292 6777; Fax: +1 614 292 8120; E-mail: artsimovitch.1@osu.edu
Dmitry G Vassylyev Tel: +1 205 975 8136; Fax: +1 205 934 0758; E-mail: dmitry@uab.edu
* Theses authors contributed equally to this work
Received 2 April 2007; Accepted 22 August 2007; Published online 5 October 2007.
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Abstract
Bacterial Gre transcript cleavage factors stimulate the intrinsic endonucleolytic activity of RNA polymerase (RNAP) to rescue stalled transcription complexes. They bind to RNAP and extend their coiled-coil (CC) domains to the catalytic centre through the secondary channel. Three existing models for the Gre–RNAP complex postulate congruent mechanisms of Gre-assisted catalysis, while offering conflicting views of the Gre–RNAP interactions. Here, we report the GreB structure of Escherichia coli. The GreB monomers form a triangle with the tip of the amino-terminal CC of one molecule trapped within the hydrophobic cavity of the carboxy-terminal domain of a second molecule. This arrangement suggests an analogous model for recruitment to RNAP. Indeed, the '-subunit CC located at the rim of the secondary channel has conserved hydrophobic residues at its tip. We show that substitutions of these residues and those in the GreB C-terminal domain cavity confer defects in GreB activity and binding to RNAP, and present a plausible model for the RNAP–GreB complex.
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