Comparative Analysis of the Regulation ofrovAfrom the Pathogenic Yersiniae

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Abstract
RovA is a MarR/SlyA-type regulator that mediates the transcription of inv in Yersinia enterocolitica and Y. pseudotuberculosis. In Y. pseudotuberculosis, rovA transcription is controlled primarily by H-NS and RovA, which bind to similar regions within the rovA promoter. At 37°C, rovA transcription is repressed by H-NS. Transcription of rovA results when RovA relieves H-NS-mediated repression. The region of the rovA promoter that H-NS and RovA bind is not conserved in the Y. enterocolitica promoter. Using green fluorescent protein reporters, we determined that the Y. enterocolitica rovA (rovAYent) promoter is weaker than the Y. pseudotuberculosis promoter. However, despite the missing H-NS/RovA binding site in the rovAYent promoter, H-NS and RovA are still involved in the regulation of rovAYent. DNA binding studies suggest that H-NS and RovA bind with a higher affinity to the Y. pseudotuberculosis/Y. pestis rovA (rovAYpstb/Ypestis) promoter than to the rovAYent promoter. Furthermore, H-NS appears to bind to two regions in a cooperative fashion within the rovAYent promoter that is not observed with the rovAYpstb/Ypestis promoter. Finally, using a transposon mutagenesis approach, we identified a new positive regulator of rovA in Y. enterocolitica, LeuO. In Escherichia coli, LeuO regulates gene expression via changes in levels of RpoS and H-NS, but LeuO-mediated regulation of rovAYent appears to be independent of either of these two proteins. Together, these data demonstrate that while the rovA regulatory factors are conserved in Yersinia, divergence of Y. enterocolitica and Y. pseudotuberculosis/Y. pestis during evolution has resulted in modifications in the mechanisms that are responsible for controlling rovA transcription.