THE HOMEODOMAIN PROTEIN PBX1 IS INVOLVED IN CAMP-DEPENDENT TRANSCRIPTION OF HUMAN CYP17

Pbx1 is a homeodomain transcription factor involved in cAMP-dependent transcriptional regulation of the bovine CYP17 gene. In this study, we have investigated the involvement of Pbx1 in the transcriptional regu lation of the human CYP17 gene, Although a sequence identical to previ ously determined Pbx-binding sites is not present in the promoter regi on of the human CYP17 gene, three putative Pbx-binding sites are ident ified by sequence similarity analysis, Coexpression of Pbx1 and a cata lytic subunit of protein kinase A (PKA) greatly enhances reporter gene transcription via the 5'-flanking region of the human CYP17 gene, Upo n gel shift analysis utilizing nuclear extracts from human adrenal H29 5R cells, one of the three putative Pbx1-binding sites, -250/-241 bp, shows the typical intense doublet observed with other Pbx-binding site s, 5'-Deletion analyses of the reporter construct containing this Pbx- binding site showed approximately sixfold induction by coexpression of Pbx1 and PKA compared to the basal transcription, suggesting that Pbx 1 binds the -250/-241 bp sequence and participates in cAMP-dependent r egulation of the human CYP17 gene. (C) 1997 Academic Press.