Direct and negative regulation of the sycO-ypkA-ypoJ operon by cyclic AMP receptor protein (CRP) in Yersinia pestis

Abstract

Background. Pathogenic yersiniae, including Y. pestis, share a type III secretion system (T3SS) that is composed of a secretion machinery, a set of translocation proteins, a control system, and six Yop effector proteins including YpkA and YopJ. The cyclic AMP receptor protein (CRP), a global regulator, was recently found to regulate the laterally acquired genes (pla and pst) in Y. pestis. The regulation of T3SS components by CRP is unknown. Results. The sycO, ypkA and yopJ genes constitute a single operon in Y. pestis. CRP specifically binds to the promoter-proximate region of sycO, and represses the expression of the sycO-ypkA-yopJ operon. A single CRP-dependent promoter is employed for the sycO-ypkA-yopJ operon, but two CRP binding sites (site 1 and site 2) are detected within the promoter region. A CRP box homologue is found in site 1 other than site 2. The determination of CRP-binding sites, transcription start site and core promoter element (-10 and -35 regions) promotes us to depict the structural organization of CRP-dependent promoter, giving a map of CRP-promoter DNA interaction for sycO-ypkA-yopJ. Conclusion. The sycO-ypkA-yopJ operon is under the direct and negative regulation of CRP in Y. pestis. The sycO-ypkA-yopJ promoter-proximate regions are extremely conserved in Y. pestis, Y. pseudotuberculosis and Y. enterocolitica. Therefore, data presented here can be generally applied to the above three pathogenic yersiniae.