A novel CsrA titration mechanism regulates fimbrial gene expression in Salmonella typhimurium.
A hierarchical control of fimbrial gene expression limits laboratory grown cultures of Salmonella enterica serovar typhimurium (S. typhimurium) to the production of type I fimbriae encoded by the fimAICDHF operon. Here we show that an unlikely culprit, namely the 5'-untranslated region (5'-UTR) of a messenger (m)RNA, coordinated the regulation. Binding of CsrA to the 5'-UTR of the pefACDEF transcript was required for expression of plasmid-encoded fimbriae. The 5'-UTR of the fimAICDHF transcript cooperated with two small untranslated RNAs, termed CsrB and CsrC, in antagonizing the activity of the RNA binding protein CsrA. Through this post-transcriptional mechanism, the 5'-UTR of the fimAICDHF transcript prevented production of PefA, the major structural subunit of plasmid-encoded fimbriae. This regulatory mechanism limits the costly expression of plasmid-encoded fimbriae to host environments in a mouse model. Collectively, our data suggest that the 5'-UTR of an mRNA coordinates a hierarchical control of fimbrial gene expression in S. typhimurium.
Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, Davis, CA, USA.
Torsten
T
Sterzenbach
Kim T
KT
Nguyen
Sean-Paul
SP
Nuccio
Maria G
MG
Winter
Christopher A
CA
Vakulskas
Steven
S
Clegg
Tony
T
Romeo
Andreas J
AJ
Bäumler
D000818:Animals; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D036781:Fimbriae Proteins / Q000235:genetics* / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D051379:Mice; D008810:Mice, Inbred C57BL; D012329:RNA, Bacterial / Q000235:genetics; D012486:Salmonella typhimurium / Q000235:genetics*
D012329:RNA, Bacterial; D036781:Fimbriae Proteins