Stress Detection Using Bioluminescent Reporters of the Heat-Shock Response

The heat-shock response is the coordinated induction of a set of protems in response to a variety of cellular stresses, including elevated temperature (1 ). Several of the induced proteins function to reactivate or degrade denatured proteins, which are the signal initiating the response. The heat-shock response, therefore, functions to maintam the proteinacious component of the cell in an active form. Thus, by inducing heat-shock protein synthesis, the cell is better able to survive the stress condition. The regulation of the heat shock response typically occurs at the transcriptional level. In Escherichia coli the heat-shock sigma factor, σ³² , drives transcription of about 20 genes (2 ). These include dnaK , encoding the molecular chaperone Hsp70, grpE , encoding a protein that interacts with Hsp70 in the protein folding pathway, and lon , a protease that degrades unfolded protems. Detection of the heat-shock response has been selected as a useful indicator of biological stress (3 –5 ) because this response is universally found in btological systems and is induced by sublethal levels of a wide variety of cellular insults.