Activation of the Drosophila hsp27 promoter by heat shock and by ecdysone involves independent and remote regulatory sequences

Abstract

Transcription of the Drosophila hsp27 gene is induced both by heat shock and by the steroid hormone ecdysone. Deletion analysis of the promoter using a transient expression assay in Drosophila tissue culture cells reveals two separate and functionally independent regulatory regions, whose positions coincide with previously reported DNase I-hypersensitive sites in embryonic chromatin. Ecdysone induction is mediated by multiple elements between -579 and -455. Several matches to the consensus heat shock regulatory element (HSE) lie between -370 and -270, and deletion of these abolishes the response to heat shock. Heat inducibility can be restored by the addition of HSE sequences from the hsp70 promoter, even when these are placed at the 3' end of the gene. Furthermore, HSEs seperated by >2 kb can interact in a cooperative way to promote transcription. Deletion of sequences adjacent to the TATA box (-40 to -154) has little effect on induction by either heat shock or ecdysone. In this respect, activation of the hsp27 TATA box in Drosophila cells differs from the long-range activation of promoters by HSEs or viral enhancers in HeLa cells.