Abstract
The regulation of the Drosophila melanogaster hsp23 gene by heat shock in injected Xenopus oocytes and by heat shock and ecdysterone in transfected hormone-sensitive Drosophila melanogaster cells has been analyzed by measuring activites of hsp-E. coli beta-galactosidase hybrid genes. Mutational analysis identified multiple, distinct promoter elements. A sequence element which also occurs in the promoters of a number of other genes that are specifically expressed in late larvae or early pupae was shown to be essential for the ecdysterone- but not for the heat-regulated activity of the hsp23 gene; this element may represent a binding site(s) for an ecdysterone-receptor complex. Mutant promoters that can only be activated either by heat shock or by hormone have been constructed. Thus, the two types of regulation of the hsp23 gene can function completely independent of each other.