Heat shock but not benzamide and colchicine response elements are present within the-844 bp upstream region of the hrsω gene of Drosophila melanogaster

Abstract

The selective inducibility of hsrω gene by heat shock and several chemical agents and its selective non-inducibility by heat shock under certain conditions led to suggestion that this locus is subject to multiple controls at the level of transcription. With a view to delimit these different control elements, transgenic lines horbouring hsrω 5' promoter deletion variants tagged to the lacZ reporter gene were used. Three different assays, viz., staining for β-galactosidase activity in different larval tissues using chromogenic X-gal substrate, [³H] uridine labelling of polytene nuclei andin situ DNA-DNA hybridization with a non-radioactive probe to polytene chrmosome spreads for checking the puffing status of the resident and the transgene in larval salivary glands, were applied to monitor the activiy of the reporter gene following different treatments. Our results showed that the - 844 bp to +107 bp sequence was sufficient for heat shock induction of the transgene in all tissues. An analysis of the base sequence of the hsrω promoter revealed the presence of three consensus heat shock elements at - 466, - 250 and at - 57 bp and of two GAGA factor binding sites at - 496 and at - 68bp within the - 844 bp region. Germline transformants carrying the - 346 bp to - 844 bp region of the hsrω promoter showed only a very weak heat shock inducibility of the reporter gene in agreement with the presence of only one of the three putative heat shock elements and one of the two GAGA factor binding sites in this region. Interestingly, neither of the transformed lines (carrying the - 844 bp to + 107 bp or the - 844 bp to -346 bp of the hsrω promoter region) showed any response of the transgene to benzamide or colchicine treatments. These results showed that while the heat shock response elements of the hsrω are included within the - 844 bp region the response elements for benzamide and colchicine treatments are outside this region.