The effect of heat shock on 20S/26S proteasomes.

We have studied the consequences of heat shock on 20S/26S proteasome activity and activation, the proteasomal subunit composition, proteasome assembly, subunit mRNA stability as well as on the intracellular distribution of proteasomes. Our data show that heat shock locks 20S proteasomes in their latent inactive state and impairs further activation of the 26S proteasome by ATP. Proteasome mRNA levels are decreased after heat shock and the assembly of the proteasome complex is inhibited. Heat shock also induces a rapid reorganisation of the cellular distribution of the proteasome which appears to be connected with proteasome activity and the change of the cellular architecture after heat shock.