CLONING OF A CHIRONOMUS-TENTANS CDNA-ENCODING A PROTEIN (CECRH) HOMOLOGOUS TO THE DROSOPHILA-MELANOGASTER ECDYSTEROID RECEPTOR (DECR)

We have cloned a cDNA sequence coding for a Chironomus tentans steroid hormone receptor homologue which exhibits extensive amino acid sequen ce co-linearity with the ecdysteroid receptor of Drosophila melanogast er (dEcR; cell 67, 59-77). The DNA-binding domain has 95% and the horm one-binding domain 75% amino acid sequence identity with the cloned dE cR. The gene for this C. tentans protein is located on chromosome 11, region 17C, as determined by in situ hybridization to polytene chromos omes of salivary glands. On Northern blots cDNA probes of the cloned g ene hybridize to polyadenylated RNA of ca 4.2 kb. The expression of th e cloned gene seems to be developmentally regulated and correlates to changes in ecdysteroid titer. Transfection of this C. tentans protein into D. melanogaster Schneider's line 2 cells leads to transcriptional interference with endogenous dEcR on an ecdysteroid-regulated promote r.