Temperature regulation of inv by RovA, YmoA and H-NS in Yersinia enterocolitica

Invasin is an outer membrane protein found in Y. enterocolitica and Y. pseudotuberculosis that is sufficient to mediate invasion of host cells. Invasin is encoded by the inv gene and is maximally expressed during in vitro growth in late exponential to early stationary phase and responds to changes in temperature and pH of the growth media. Three proteins that have been shown to regulate inv transcription are RovA, which is required for inv activation and YmoA and H-NS, which are involved in the repression of inv. RovA and H-NS specifically bind the inv promoter and preferentially interact with the same segments of the promoter. RovA and H-NS are able to displace one another from the inv promoter in vitro, suggesting that RovA and H-NS are directly competing for the same binding sites. Removal of the H-NS/RovA binding sites from the inv promoter results in inv activation independent of RovA, suggesting that RovA is acting as a derepressor. While YmoA is required for repression of inv, it does not specifically recognize the inv promoter. YmoA negatively affects the expression of inv through direct interaction with H-NS, with H-NS supplying the binding specificity for the complex. Levels of hns and ymoA transcripts are similar between 26°C and 37°C suggesting that the H-NS/YmoA repression complex is present at both temperatures, while the levels of rovA are low at 37°C and high at 26°C. Exogenous expression of RovA at 37°C results in activation of inv transcription suggesting that levels of RovA are critical for overcoming repression of inv transcription. Data presented here support a model of inv regulation where the level of RovA within the cell governs inv expression. As RovA levels increase, RovA can successfully compete for binding to the inv promoter with the H-NS/YmoA complex resulting in derepression of inv transcription.