DELETION ANALYSIS OF CSPA OF ESCHERICHIA-COLI - REQUIREMENT OF THE AT-RICH UP ELEMENT FOR CSPA TRANSCRIPTION AND THE DOWNSTREAM BOX IN THE CODING REGION FOR ITS COLD SHOCK INDUCTION

In order to analyse the mechanism of cold shock induction of CspA, a m ajor cold shock protein of Escherichia coli, deletion analysis of the cspA gene was carried out. It was found that (i) the AT-rich sequence (-47 to -38) upstream of the cspA -35 region may act as the UP element playing a crucial role in cspA transcription at both 37 degrees C and 15 degrees C; (ii) the unusually long 5'-UTR of the cspA mRNA has neg ative effects on cspA expression at 37 degrees C; and (iii) in contras t, the 5'-UTR exerts a positive effect on mRNA stabilization at low te mperature. Furthermore, it was demonstrated that the 14 base downstrea m box (DB) locating 12 bases downstream of the initiation codon of the cspA mRNA and complementary to a region near the decoding region of 1 6S rRNA was essential for the mRNA translation during the growth lag a cclimation phase immediately after cold shock. During this phase, tran slation of non-cold shock gene mRNAs is blocked, since they require co ld shock-specific ribosomal factors for the formation of the translati on initiation complex. It is proposed that DB in cold shock mRNAs allo ws the formation of a stable initiation complex at low temperature in the absence of the cold shock ribosomal factors.