TY - JOUR

T1 - RflM mediates target specificity of the RcsCDB phosphorelay system for transcriptional repression of flagellar synthesis in Salmonella enterica

AU - Kühne, Caroline

AU - Singer, Hanna M.

AU - Grabisch, Eva

AU - Codutti, Luca

AU - Carlomagno, Teresa

AU - Scrima, Andrea

AU - Erhardt, Marc

N1 - We are grateful to Hagen Richter for help with the analytical gel filtration, Kelly T. Hughes for generous strain donation and constant support, Nadine Körner for expert technical assistance and members of the Erhardt lab for useful discussions of the manuscript. This work was funded by the Helmholtz Association Young Investigator grant number VH-NG-932 (to M.E.), VH-NG-727 (to A.S.), the People Programme (Marie Curie Actions) of the Europeans Unions' Seventh Framework Programme grant number 334030 (to M.E.) and the Leibniz University Hannover (to L.C. and T.C.). C.K. gratefully acknowledges support by the President's Initiative and Networking Funds of the Helmholtz Association of German Research Centers (HGF) under contract number VH-GS-202. H.M.S. acknowledges scholarship support of the Boehringer Ingelheim Fonds.

PY - 2016/8/25

Y1 - 2016/8/25

N2 - The bacterial flagellum enables directed movement of Salmonella enterica towards favorable conditions in liquid environments. Regulation of flagellar synthesis is tightly controlled by various environmental signals at transcriptional and post-transcriptional levels. The flagellar master regulator FlhD4C2 resides on top of the flagellar transcriptional hierarchy and is under autogenous control by FlhD4C2-dependent activation of the repressor rflM. The inhibitory activity of RflM depends on the presence of RcsB, the response regulator of the RcsCDB phosphorelay system. In this study, we elucidated the molecular mechanism of RflM-dependent repression of flhDC. We show that RcsB and RflM form a heterodimer that coordinately represses flhDC transcription independent of RcsB phosphorylation. RcsB-RflM complex binds to a RcsB box downstream the P1 transcriptional start site of the flhDC promoter with increased affinity compared to RcsB in the absence of RflM. We propose that RflM stabilizes binding of unphosphorylated RcsB to the flhDC promoter in absence of environmental cues. Thus, RflM is a novel auxiliary regulatory protein that mediates target specificity of RcsB for flhDC repression. The cooperative action of the RcsB-RflM repressor complex allows Salmonella to fine-tune initiation of flagellar gene expression and adds another level to the complex regulation of flagellar synthesis.

AB - The bacterial flagellum enables directed movement of Salmonella enterica towards favorable conditions in liquid environments. Regulation of flagellar synthesis is tightly controlled by various environmental signals at transcriptional and post-transcriptional levels. The flagellar master regulator FlhD4C2 resides on top of the flagellar transcriptional hierarchy and is under autogenous control by FlhD4C2-dependent activation of the repressor rflM. The inhibitory activity of RflM depends on the presence of RcsB, the response regulator of the RcsCDB phosphorelay system. In this study, we elucidated the molecular mechanism of RflM-dependent repression of flhDC. We show that RcsB and RflM form a heterodimer that coordinately represses flhDC transcription independent of RcsB phosphorylation. RcsB-RflM complex binds to a RcsB box downstream the P1 transcriptional start site of the flhDC promoter with increased affinity compared to RcsB in the absence of RflM. We propose that RflM stabilizes binding of unphosphorylated RcsB to the flhDC promoter in absence of environmental cues. Thus, RflM is a novel auxiliary regulatory protein that mediates target specificity of RcsB for flhDC repression. The cooperative action of the RcsB-RflM repressor complex allows Salmonella to fine-tune initiation of flagellar gene expression and adds another level to the complex regulation of flagellar synthesis.

UR - http://www.scopus.com/inward/record.url?scp=84983605211&partnerID=8YFLogxK

U2 - 10.1111/mmi.13427

DO - 10.1111/mmi.13427

M3 - Article

C2 - 27206164

AN - SCOPUS:84983605211

VL - 101

SP - 841

EP - 855

JO - Molecular microbiology

JF - Molecular microbiology

SN - 0950-382X

IS - 5

ER -