Characterization of heat shock factor transactivation during heat shock in Drosophila

Cells elicit defense mechanisms to counteract stresses. One example is the heat shock response that is activated by heat shock factor (HSF), which stimulates the transcription of genes encoding the cytoprotective heat shock proteins. In the present study, two aspects of HSF transactivation were characterized in Drosophila SL2 cells. The first examined processes involved in HSF regulation. Studies using geldanamycin, an hsp83 inhibitor, showed that hsp83 is implicated in the negative regulation of HSF and that HSF hyperphosphorylation is unnecessary for its acquisition of transcriptional competence. In the second focus, a consequence of HSF transactivation was addressed. During heat shock, the transcription of most non-heat shock genes is repressed in Drosophila . Using an HSF truncation mutant, the repression of a non-heat shock gene, histone H1, was demonstrated to be associated with HSF and its transactivation domain. Evidently, multi-faceted regulatory processes are associated with HSF transactivation during the heat shock response.