The cells of an organisms respond to mild temperature elevation (and many other forms of stress) by synthesizing a small group of highly conserved proteins called the heat-shock proteins (hsps). A good deal of indirect evidence suggests that these proteins provide protection from the toxic effects of heat, but little is known about their specific molecular functions. Recent work has shown that some of these proteins are induced during the normal course of development, a finding that suggests they may play important roles in normal cellular processes, as well as during exposure to stress. The experiments outlined in this proposal focus on the heat- shock response of the fruit fly, Drosophila melanogester. They address two major issues: what are the functions of the hsps, and how is their synthesis regulated? Specifically, we seek answers to the following: What features of the heat shock genes (in addition to the heat shock consensus elements) are required for proper transcriptional regulation? What is the effect of heat and of heat shock proteins on RNA processing? Which heat-shock proteins are involved in regulating the response and in conferring upon the cell resistance to high temperatures? With what molecules do hsps associate, and how do their associations relate to its cellular functions?