Transcription of cspA, the gene for the major cold-shock protein of Escherichia coli, is negatively regulated at 37 degrees C by the 5'-untranslated region of its mRNA.

The gene for CspA, the major cold-shock protein in Escherichia coli, is tightly regulated at both optimal and low temperatures. While CspA is drastically induced after temperature downshift, it is hardly detectable at 37 degrees C. Here we demonstrate that the deletion of parts of the 5'-untranslated region (5'-UTR) of the cspA mRNA results in constitutive expression of CspA at 37 degrees C. By analyzing the amounts and the stabilities of the mRNAs produced from the deletion constructs, we rule out the possibility that the CspA production is due to the stabilization of the mutant mRNAs. We propose that significant premature termination or pausing occurs during the transcription of the unusually long 5'-UTR of the cspA mRNA at 37 degrees C, which represents a new mechanism that contributes to the tight repression of CspA production at higher temperature.