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Two antisense RNAs target the transcriptional regulator CsgD to inhibit curli synthesis
Author(s) -
Holmqvist Erik,
Reimegård Johan,
Sterk Maaike,
Grantcharova Nina,
Römling Ute,
Wagner Eduard Gerhart Heinrich
Publication year - 2010
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2010.73
Subject(s) - molecular cell biology , biology , library science , microbiology and biotechnology , computer science
Escherichia coli produces proteinaceous surface structures called curli that are involved in adhesion and biofilm formation. CsgD is the transcriptional activator of curli genes. We show here that csgD expression is, in part, controlled post‐transcriptionally by two redundant small RNAs (sRNAs), OmrA and OmrB. Their overexpression results in curli deficiency, in accordance with the inhibition of chromosomally encoded, FLAG‐tagged CsgD. Downregulation of csgD occurs by a direct antisense interaction within the csgD 5′‐UTR, far upstream of the ribosome‐binding site (RBS). OmrA/B downregulate plasmid‐borne csgD‐gfp fusions in vivo , and inhibit CsgD translation in vitro . The RNA chaperone Hfq is required for normal csgD mRNA and OmrA/B levels in the cell, and enhances sRNA‐dependent inhibition of csgD translation in vitro . Translational inhibition involves two phylogenetically conserved secondary structure modules that are supported by chemical and enzymatic probing. The 5′‐most element is necessary and sufficient for regulation, the one downstream comprises the RBS and affects translational efficiency. OmrA/B are two antisense RNAs that regulate a transcription factor to alter a morphotype and group behaviour.