Talk abstracts

Talk on Saturday 12:30-12:50pm submitted by Irina Artsimovitch

Division of labor between transcription elongation factors

Irina Artsimovitch (Department of Microbiology and The RNA Group, The Ohio State University), Georgiy A. Belogurov (Department of Microbiology and The RNA Group, The Ohio State University)

Abstract:
Transcription elongation factors NusG and RfaH evolved from a common ancestor and utilize the same binding site on RNA polymerase to modulate transcription. Both proteins increase the rate of RNA synthesis in vitro. However, ChIP-chip analysis indicates that while NusG associates with RNA polymerase transcribing most E. coli genes, RfaH action is restricted to several operons that are devoid of NusG and contain an ops element, a DNA sequence that mediates RfaH recruitment (1). In vitro assays reveal that RfaH and NusG compete for their effects on transcript elongation and termination. Our data argue that RfaH recognizes its specific DNA target even in the presence of NusG. Once recruited, RfaH remains stably associated with RNA polymerase, thereby precluding NusG binding. We propose that E. coli RfaH and NusG play opposite regulatory roles. NusG acts in concert with Rho to suppress expression of foreign DNA (2). By contrast, RfaH inhibits Rho action and activates expression of poorly translated, frequently laterally transferred genes. We envision a pathway by which a specialized regulator has evolved in the background of its ubiquitous paralog.

References:
1. Belogurov, G. A., Mooney, R. A., Svetlov, V., Landick, R. & Artsimovitch, I. (2009). Functional specialization of transcription elongation factors. EMBO J 28, 112-22.

2. Cardinale, C. J., Washburn, R. S., Tadigotla, V. R., Brown, L. M., Gottesman, M. E. & Nudler, E. (2008). Termination factor Rho and its cofactors NusA and NusG silence foreign DNA in E. coli. Science 320, 935-8.

Keywords: transcription, termination, regulation