Reciprocal regulation of pH 6 antigen gene loci by PhoP and RovA in Yersinia pestis biovar Microtus.

Aim: To explore the transcriptional regulation of the psaEF and psaABC loci by the RovA and PhoP regulators in Yersinia pestis.
Materials & Methods: Primer extension, LacZ fusion, gel mobility shift and DNase I footprinting assays were conducted in combination for this gene regulation study.
Results: It was determined that PhoP and RovA recognized the promoter-proximal regions of psaEF and psaABC in order to repress and stimulate their transcription, respectively. The translation/transcription start sites, Shine-Dalgarno sequences (ribosomal binding site), core promoter -10 and -35 elements, PhoP and RovA sites and PhoP/RovA consensus-like sequences were identified to determine the structural organization of PhoP/RovA-dependent promoters of psaEF and psaABC.
Conclusion: RovA stimulated psaEF and psaABC, while PhoP repressed these two operons involving the direct association between RovA/PhoP and target promoter regions. The reciprocal regulation of psa genes by PhoP and RovA could contribute to the tightly controlled expression of the pH 6 antigen during infection.