THE GROESL OPERON OF AGROBACTERIUM-TUMEFACIENS - EVIDENCE FOR HEAT SHOCK-DEPENDENT MESSENGER-RNA CLEAVAGE

The heat shock response of the groESL operon of Agrobacterium tumefaci ens was studied at the RNA level, The operon was found to be activated under heat shock conditions and transcribed as a polycistronic mRNA t hat contains the groES and groEL genes. After activation, the polycist ronic mRNA appeared to be cleaved between the groES and groEL genes an d formed two monocistronic mRNAs, The groES cleavage product appeared to be unstable and subjected to degradation, while the groEL cleavage product appeared to be stable and became the major mRNA representing t he groESL operon after long periods of growth at a high temperature, T he polycistronic mRNA containing the groES and groEL genes was the maj or mRNA representing the groESL operon at a low temperature, and it re appeared when the cells were returned to the lower growth temperature after heat shock induction, These findings indicate that the cleavage event is part of the heat shock regulation of the groESL operon in A. tumefaciens.