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J. Bacteriol., 11 1997, 7081-7088, Vol 179, No. 22
W Bae, PG Jones and M Inouye
When the gene for CspA, the major cold shock protein of Escherichia coli,
was disrupted by a novel positive/negative selection method, the deltacspA
cells did not show any discernible growth defect at either 37 or 15 degrees
C. By two-dimensional gel electrophoresis, total protein synthesis was
analyzed after temperature downshift in the deltacspA strain. The
production of the CspA homologs CspB and CspG increased, and the duration
of their expression was prolonged, suggesting that both CspB and CspG
compensate for the function of CspA in the absence of CspA during cold
shock adaptation. Interestingly, the production of the 159-base
5'-untranslated region (5'-UTR) of cspA from the chromosomal cspA::cat
gene, detected by primer extension, failed to be repressed after cold
shock. When an independent system to produce CspA was added to the
deltacspA strain, the 5'-UTR production for the cspA::cat gene was
significantly reduced compared to that of the deltacspA strain. By
examining the expression of translationally fused cspA and cspB genes to
lacZ in the deltacspA strain, it was found that cspA is more strongly
regulated by CspA than cspB is. We showed that the increased expression of
the 5'-UTR of the cspA mRNA in the deltacspA strain occurred mainly at the
level of transcription and, to a certain extent, at the level of mRNA
stabilization. The mRNA stabilization in the deltacspA strain was observed
for other mRNAs, supporting the notion that CspA functions as an mRNA
chaperone to destabilize secondary structures in mRNAs.
Copyright © 1997, American Society for Microbiology
CspA, the major cold shock protein of Escherichia coli, negatively regulates its own gene expression
Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
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