AUTOREGULATION OF THE ESCHERICHIA-COLI HEAT-SHOCK RESPONSE BY THE DNAK AND DNAJ HEAT-SHOCK PROTEINS

All organisms respond to various forms of stress, including heat shock . The heat shock response has been universally conserved from bacteria to humans. In Escherichia coli the heat shock response is under the p ositive transcriptional control of the sigma32 polypeptide and involve s transient acceleration in the rate of synthesis of a few dozen genes . Three of the heat shock genes-dnaK, dnaJ, and grpE-are special becau se mutations in any one of these lead to constitutive levels of heat s hock gene expression, implying that their products negatively autoregu late their own synthesis. The DnaK, Dnaj, and GrpE proteins have been known to function in various biological situations, including bacterio phage lambda replication. Here, we report the formation of an ATP hydr olysis-dependent complex of DnaJ, sigma32, and DnaK proteins in vitro. This DnaJ-sigma32-DnaK complex has been seen under different conditio ns, including glycerol gradient sedimentation and co-immunoprecipitati on. The DnaK and DnaJ proteins in the presence of ATP can interfere wi th the efficient binding of sigma32 to the RNA polymerase core, and ar e capable of disrupting a preexisting sigma32-RNA polymerase complex. Our results suggest a possible mechanism for the autoregulation of the heat shock response.