Highly divergent RfaH orthologs from pathogenic proteobacteria can substitute for Escherichia coli RfaH both in vivo and in vitro.
The transcriptional enhancer protein RfaH positively regulates production of virulence factors in Escherichia coli and Salmonella enterica serovar Typhimurium via a cis element, ops. Genes coding for RfaH orthologs were identified in conceptually translated genomes of bacterial pathogens, including Vibrio and Yersinia spp. We cloned the rfaH genes from Vibrio cholerae, Yersinia enterocolitica, S. enterica serovar Typhimurium, and Klebsiella pneumoniae into E. coli expression vectors. Purified RfaH orthologs, including the most divergent one from V. cholerae, were readily recruited to the E. coli transcription elongation complex. Postrecruitment stimulation of transcript elongation appeared to vary with the degree of similarity to E. coli RfaH. V. cholerae RfaH was particularly defective in reducing downstream pausing and termination; this defect was substantially alleviated by an increase in its concentration. When overexpressed episomally, all of the rfaH genes complemented the disruption of the chromosomal copy of the E. coli gene. Thus, despite the apparently accelerated divergent evolution of the RfaH proteins, the mechanism of their action is conserved well enough to make them transcriptionally active in the E. coli system.
Carter
Heather D
HD
Department of Microbiology, The Ohio State University, 376 BioSciences Building, 484 West 12th Avenue, Columbus, OH 43210, USA.
Svetlov
Vladimir
V
Artsimovitch
Irina
I
D000595:Amino Acid Sequence; D012321:DNA-Directed RNA Polymerases / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000502:physiology; D006460:Hemolysin Proteins / Q000096:biosynthesis; D008969:Molecular Sequence Data; D010445:Peptide Elongation Factors / Q000502:physiology*; D020560:Proteobacteria / Q000235:genetics*; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic; D014734:Vibrio cholerae / Q000235:genetics
D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C070291:NusG protein, E coli; D010445:Peptide Elongation Factors; C106401:RfaH protein, E coli; D015534:Trans-Activators; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases