PROMOTER-INDEPENDENT COLD-SHOCK INDUCTION OF CSPA AND ITS DEREPRESSION AT 37-DEGREES-C BY MESSENGER-RNA STABILIZATION

The gene for CspA, the major cold-shock protein of Escherichia coli is known to be dramatically induced upon temperature downshift. Here, we report that three-base substitutions around the Shine-Dalgarno sequen ce in the 159-base 5'-untranslated region of the cspA mRNA stabilizes the mRNA 150-fold, resulting in constitutive expression of cspA at 37 degrees C. This stabilization was found to be at least partially due t o resistance against RNase E degradation. The cold-shock induction of cspA was also achieved by exchanging its promoter with the non-cold-sh ock Ipp promoter. The results presented indicate that the cspA gene is efficiently transcribed even at 37 degrees C. However, the translatio n of the cspA mRNA is blocked because of its extreme instability at 37 degrees C. The presented results also demonstrate that the cspA gene is constitutively transcribed at all temperatures; however, its expres sion at 37 degrees C is prevented by destabilizing its mRNA.