title: Induction of sequence-specific binding of Drosophila heat shock activator protein without protein synthesis.
abstract: Drosophila tissue culture cells stimulated by heat shock contain high levels of heat shock activator protein, which binds specifically to the heat-shock control DNA element. In contrast, nonshocked cells have low basal levels of binding activity. Here, we show that within 30 seconds of heat shock of intact cells the sequence-specific binding activity in whole cell extracts increases significantly, reaching a plateau by 5 min after the start of the shock; removal of the heat stimulus returns the activity to basal levels. Known chemical inducers of heat-shock genes elicit a similar pattern of specific binding activity. Moreover, this pattern is observed in the presence of protein synthesis inhibitors, even if the stimulus-withdrawal is repeated sequentially through five cycles. Our results are inconsistent with models which propose proteolysis as the chief means of mediating heat-shock transcriptional control. Rather, they suggest that heat shock activator pre-exists in normal cells in a nonbinding form, which is converted upon cell stimulus to a high affinity, sequence-specific binding form, most probably by a post-translational modification. This conversion may be crucial for the transcriptional activation of heat shock genes.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004140:Dinitrophenols / Q000494:pharmacology; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D006358:Hot Temperature; D007700:Kinetics; D011506:Proteins / Q000378:metabolism*; D012980:Sodium Salicylate / Q000494:pharmacology; D014157:Transcription Factors; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D004140:Dinitrophenols; D029721:Drosophila Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; C053134:Hsf protein, Drosophila; D011506:Proteins; D014157:Transcription Factors; D004247:DNA; D012980:Sodium Salicylate