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Complex regulation of the global regulatory gene csrA : CsrA‐mediated translational repression, transcription from five promoters by Eσ 70 and Eσ S , and indirect transcriptional activation by CsrA
Author(s) -
Yakhnin Helen,
Yakhnin Alexander V.,
Baker Carol S.,
Sineva Elena,
Berezin Igor,
Romeo Tony,
Babitzke Paul
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07723.x
Subject(s) - biology , psychological repression , transcription (linguistics) , primer extension , promoter , regulation of gene expression , repressor , microbiology and biotechnology , transcriptional regulation , sigma factor , genetics , gene expression , gene , messenger rna , linguistics , philosophy
Summary CsrA of Escherichia coli is an RNA‐binding protein that globally regulates gene expression by repressing translation and/or altering the stability of target transcripts. Here we explored mechanisms that control csrA expression. Four CsrA binding sites were predicted upstream of the csrA initiation codon, one of which overlapped its Shine–Dalgarno sequence. Results from gel shift, footprint, toeprint and in vitro translation experiments indicate that CsrA binds to these four sites and represses its own translation by directly competing with 30S ribosomal subunit binding. Experiments were also performed to examine transcription of csrA . Primer extension, in vitro transcription and in vivo expression studies identified two σ 70 ‐dependent (P2 and P5) and two σ S ‐dependent (P1 and P3) promoters that drive transcription of csrA . Additional primer extension studies identified a fifth csrA promoter (P4). Transcription from P3, which is indirectly activated by CsrA, is primarily responsible for increased csrA expression as cells transition from exponential to stationary‐phase growth. Taken together, our results indicate that regulation of csrA expression occurs by a variety of mechanisms, including transcription from multiple promoters by two sigma factors, indirect activation of its own transcription, as well as direct repression of its own translation.