The LysR-type transcriptional regulator VirR is required for expression of the virulence gene vapA of Rhodococcus equi ATCC 33701.
The virulence of the intracellular pathogen Rhodococcus equi in foals is dependent on the presence of an 81-kb virulence plasmid encoding the virulence protein VapA. Expression of this protein is induced by exposure to oxidative stress, high temperatures, and low pHs, which reflect the conditions encountered by R. equi when it enters the host environment. The aim of this study was to determine whether the LysR-type transcriptional regulator VirR, which is encoded by the virulence plasmid, is required for the expression of vapA. It was shown that the virR gene is cotranscribed with four downstream genes, one of which encodes a two-component response regulator. The expression of VapA, as monitored by Western blotting, was completely dependent on the presence of virR. Maximal expression was observed when vapA was present together with the complete virR operon, suggesting that at least one of the virR operon genes, in addition to virR, is required for the expression of vapA to wild-type levels. The transcriptional start site of vapA was determined to be a cytidine located 226 bp upstream from the vapA initiation codon. His-tagged VirR protein was expressed in Escherichia coli and purified by nickel affinity chromatography. DNA binding studies showed that purified VirR binds to a DNA fragment containing the vapA promoter. We therefore conclude that VirR is required for the activation of vapA transcription.
Department of Industrial Microbiology, University College Dublin, Dublin 4, Ireland.
Dean A
DA
Russell
Gavin A
GA
Byrne
Enda P
EP
O'Connell
Clara A
CA
Boland
Wim G
WG
Meijer
D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics*; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D009876:Operon; D018384:Oxidative Stress; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D016929:Rhodococcus equi / Q000235:genetics* / Q000378:metabolism; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics*; D037521:Virulence Factors / Q000096:biosynthesis* / Q000235:genetics*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D014157:Transcription Factors; D037521:Virulence Factors