Autoregulation of PhoP/PhoQ and Positive Regulation of the Cyclic AMP Receptor Protein-Cyclic AMP Complex by PhoP in Yersinia pestis

Abstract

Yersinia pestis is one of the most dangerous bacterial pathogens. PhoP and cyclic AMP receptor protein (CRP) are global regulators of Y. pestis, and they control two distinct regulons that contain multiple virulence-related genes. The PhoP regulator and its cognate sensor PhoQ constitute a two-component regulatory system. The regulatory activity of CRP is triggered only by binding to its cofactor cAMP, which is synthesized from ATP by adenylyl cyclase (encoded by cyaA). However, the association between the two regulatory systems PhoP/PhoQ and CRP-cAMP is still not understood for Y. pestis. In the present work, the four consecutive genes YPO1635, phoP, phoQ, and YPO1632 were found to constitute an operon, YPO1635-phoPQ-YPO1632, transcribed as a single primary RNA, whereas the last three genes comprised another operon, phoPQ-YPO1632, transcribed with two adjacent transcriptional starts. Through direct PhoP-target promoter association, the transcription of these two operons was stimulated and repressed by PhoP, respectively; thus, both positive autoregulation and negative autoregulation of PhoP/PhoQ were detected. In addition, PhoP acted as a direct transcriptional activator of crp and cyaA. The translational/transcriptional start sites, promoter ؊10 and ؊35 elements, PhoP sites, and PhoP box-like sequences were determined for these PhoP-dependent genes, providing a map of the PhoP-target promoter interaction. The CRP and PhoP regulons have evolved to merge into a single regulatory cascade in Y. pestis because of the direct regulatory association between PhoP/PhoQ and CRP-cAMP.

Posttranscriptional Regulation of the Yersinia pestis Cyclic AMP Receptor Protein Crp and Impact on Virulence

“…In addition, Zhang et al recently showed that the two-component response regulator PhoP directly activates the transcription of both crp and cyaA (33). Thus, considering the distinct environments that Y. pestis inhabits compared to E. coli or even other bacterial pathogens, these data suggest the possibility that divergent mechanisms of crp regulation have evolved that are specific or unique to Yersinia species.…”

A direct link between the global regulator PhoP and the Csr regulon inY. pseudotuberculosisthrough the small regulatory RNA CsrC

“…28 Moreover, Y. pestis PhoP was shown to activate crp expression in rich medium. 29 However, in contrast to Y. pestis, PhoP does not affect crp expression and Crp levels in Y. pseudotuberculosis when cultured in rich medium. The species-specific differences are surprising, since the crp, csrB, csrC, and the rovA promoter regions are highly conserved between Y. pestis and Y. pseudotuberculosis, 55,56 indicating that different regulator variants or other regulatory elements participate in the control of the Csr system in different yersiniae.…”

“…1). 28,29 In order to test the role of PhoP in Y. pseudotuberculosis, we first investigated the influence of the response regulator on RovA expression in the wild-type strains YPIII and IP32953. Both strains have most frequently been used to elucidate Y. pseudotuberculosis pathogenicity.…”

“…Several genes, which are involved in detoxification, protection against DNA damage, resistance to antimicrobial peptides, and adaptation to magnesium limitation (e.g., mgtCB that encodes a Mg 2+ transport system) were proven to be direct targets of PhoP. 9,27,28 Recent studies further showed that PhoP of Y. pestis biovar Microtus also acts as direct activator of crp and as repressor of the rovA, psaEF, and psaABC loci, 28,29 which are all part of a complex regulatory cascade characterized in the close relative Y. pseudotuberculosis (Fig. 1).…”

The Cyclic AMP Receptor Protein Regulates Quorum Sensing and Global Gene Expression in Yersinia pestis During Planktonic Growth and Growth in Biofilms

“…Other proteins can regulate expression of the crp gene, suggesting that multiple input signals modulate expression of the Crp regulon. The two-component system PhoPQ and the small RNA chaperone Hfq regulate crp in Y. pestis (6,20,21). In turn, Crp regulates expression of the type III secretion system and the Pla protease essential for pneumonic plague (22)(23)(24).…”