Heat shock-induced repression of proteolysis: poly(A)-binding protein degradation patterns can illusorily suggest its specific loss during heat shock

Poly(A)-binding protein (PABP) is highly susceptible to proteolysis during cell lysis of Drosophila tissue culture cells unless substantial amounts of proteolysis inhibitors are included in the extraction buffer. This intrinsic proteolytic activity is substantially reduced during heat shock. An artifactual appearance that poly(A)-binding protein is specifically degraded by heat shock can result. Several contradictory descriptions of PABP may also be related to its proteolysis. Repression of proteolysis is likely to reflect a physiologically significant regulatory event, based on recent examinations of HSP70 stability during and after heat shock.