SEQUENCE AND DEVELOPMENTAL EXPRESSION OF CYP18, A MEMBER OF A NEW CYTOCHROME-P450 FAMILY FROM DROSOPHILA

Preliminary studies of a partial cDNA clone of the Eig17-1 gene from D iosophila melanogaster have shown that it encodes a probable cytochrom e P450 of unknown function. To further characterize the Eig17-1 gene p roduct, a full-length cDNA clone was Isolated from a late-larval cDNA library and sequenced. Eig17-1 encodes a protein of 538 amino acids. T he predicted protein is a cytochrome P350 that has been assigned to a new family, CYP18. The CYP18 protein is most closely related to steroi d and xenobiotic metabolizing P450s of family CYP2 (30-33%, identity), and to vertebrate steroidogenic P450s of families CYP17 and CYP21 (25 -28% identity). Developmental Northern blot analysis revealed five dis tinct periods of Cyp18 expression during postembryonic development. Ea ch period lasted 12-15 h, and was tightly correlated with reported ecd ysteroid pulses in the first, second and third larval instars: at the time of pupariation and in pupae. This pattern of expression is consis tent with the known induction of Cyp18 transcription by 20-hydroxyecdy sone at the time of pupariation and suggests that ecdysteroids are maj or regulators of Cyp18 expression throughout postembryonic development . Northern blot analysis of RNA isolated from different prepupal tissu es indicates that Cyp18 is differentially expressed in various ecdyste roid-responsive tissues. High Cyp18 expression was observed in body wa ll and gut while negligible expression was observed in salivary glands and fat body. (C) 1997 Elsevier Science Ireland Ltd.