Journal
NUCLEIC ACIDS RESEARCH
Volume 38, Issue 12, Pages 3936-3951Publisher
OXFORD UNIV PRESS
DOI: 10.1093/nar/gkq177
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Funding
- National Science Council of the Republic of China [NSC 95-2311-B-010 -017 -MY3]
- National Institutes of Health [MCB059969]
- Aim for Top University Plan for National Yang-Ming University
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R01GM059969] Funding Source: NIH RePORTER
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Carbon storage regulator (CsrA) is a eubacterial RNA-binding protein that acts as a global regulator of many functionally diverse chromosomal genes. Here, we reveal that CsrA represses expression from an extrachromosomal element of Escherichia coli, the lysis gene (cel) of the ColE7 operon (cea-cei-cel). This operon and colicin expression are activated upon SOS response. Disruption of csrA caused similar to 5-fold increase of the lysis protein. Gel mobility shift assays established that both the single-stranded loop of the T1 stem-loop distal to cei, and the putative CsrA binding site overlapping the Shine-Dalgarno sequence (SD) of the cel gene are important for CsrA binding. Substitution mutations at SD relieved CsrA-dependent repression of the cel gene in vivo. Steady-state levels and half-life of the cel mRNA were not affected by CsrA, implying that regulation is mediated at the translational level. Levels of CsrB and CsrC sRNAs, which bind to and antagonize CsrA, were drastically reduced upon induction of the SOS response, while the CsrA protein itself remained unaffected. Thus, CsrA is a transacting modulator that downregulates the expression of lysis protein, which may confer a survival advantage on colicinogenic E. coli under environment stress conditions.
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