YopD and LcrH Regulate Expression of Yersinia enterocolitica YopQ by a Posttranscriptional Mechanism and Bind to yopQ RNA

Abstract

Pathogenic yersiniae secrete 14 Yop proteins via the type III pathway. Synthesis of YopQ occurs when the type III machinery is activated by a low-calcium signal, but not when the calcium concentration is above 100 M. To characterize the mechanism that regulates the expression of yopQ, mutants that permit synthesis of YopQ in the presence of calcium were isolated. Yersiniae bearing deletion mutations in yopN, tyeA, sycN, or yscB synthesized and secreted YopQ in both the presence and the absence of calcium. In contrast, yersiniae with a deletion in yopD or lcrH synthesized YopQ in the presence of calcium but did not secrete the polypeptide. These variants displayed no defect in YopQ secretion under low-calcium conditions, revealing that yopD and lcrH are required for the regulation of yopQ expression. Experiments with transcriptional and translational fusions to the npt reporter gene suggest that yopD and lcrH regulate yopQ expression at a posttranscriptional step. YopD and LcrH form a complex in the bacterial cytosol and bind yopQ mRNA. Models that can account for posttranscriptional regulatory mechanisms of yop expression are discussed.

Control of gene expression by type III secretory activity

“…Prior to activation of injectisome-dependent secretion by host cell contact, however, a complex consisting of LcrH (also called SycD) and YopD binds to the 5′ untranslated region of yop mRNAs and represses translation ( Fig. 2A) [36,37]. LcrH also functions as a type III chaperone for YopB and YopD (secreted translocator proteins) [38,39].…”

Dissection of homologous translocon operons reveals a distinct role for YopD in type III secretion by Yersinia pseudotuberculosis

“…The regulatory defects associated with loss of YopD and/or LcrH are consistent with the requirement of a YopD-LcrH complex to maintain yop-regulatory control (Anderson et al, 2002;Francis et al, 2001). In view of this, we investigated whether PopD (pJEB44) or PopD and PcrH (pJEB53) could complement the TS phenotype displayed by the DyopD (YPIII/pIB621) or DlcrH yopD (YPIII/pIB621H) deletion mutants, respectively (Table 2).…”

“…On the other hand, Yersinia defective for YopD constitutively produce Yop proteins and LcrV (Francis & Wolf-Watz, 1998;Williams & Straley, 1998). However, this phenotype depends on a complex between YopD and LcrH (Anderson et al, 2002;Francis et al, 2001), a specialized type III secretion chaperone that ensures the pre-secretory stabilization and efficient secretion of both YopB and YopD (Francis et al, 2000;Neyt & Cornelis, 1999b;Wattiau et al, 1994). These regulatory and translocase components are encoded by the lcrGVHyopBD polycistronic translocase operon, reflecting their common functional themes (Bergman et al, 1991).…”

RNA Regulators: Formidable Modulators of Yersinia Virulence

“…In addition to the conserved ribosomal and translation proteins, the Yersinia-specific translocon protein YopD has a RNA-binding function [50,51]. YopD (possibly alone or in complex with its secretion chaperone LcrH) was found to bind yop-encoding mRNAs in the 5'-UTRs reducing their translation either by an increase of yop mRNA degradation or hindering translation initiation [51].…”