Temporal Regulation of aTyphimurium Virulence Factor by the Transcriptional Regulator YdcR.

Abstract

We previously examinedproteome within infected host cells and found differential expression of many proteins with defined functional roles such as metabolism or virulence. However, the precise roles of other altered proteins inpathogenesis are largely unknown. A putative transcriptional regulator, YdcR, was highly induced intracellularly whereas barely expressed, implicating potential relevance to bacterial infection. To unveil its physiological functions, we exploited quantitative proteomics of intracellularand found that genetic ablation ofresulted in severe repression of SrfN, a known virulence factor. Immunoblotting, qRT-PCR, and β-galactosidase assays further demonstrate YdcR-dependent transcription and expression ofMoreover, we found physical interaction of YdcR with the promoter region of, suggesting direct activation of its transcription. Importantly, amutant lackingwas markedly attenuated in a mouse model of infection. Our findings reveal that YdcR temporally regulates the virulence factor SrfN during infection, thus contributing topathogenesis. Our work also highlights the utility of combining quantitative proteomics and bacterial genetics for uncovering the functional roles of transcription factors and likely other uncharacterized proteins as well.