Pit-1 mediates cell-specific and cAMP-induced transcription of the tilapiaGH gene

Expression of the tilapia growth hormone (tiGH) gene is pituitary-specific and controlled by intracellular cAMP levels. DNasel protection experiments allowed us to identify four Pit-1 binding sites in the tiGH -465/ +19 regio n. Deletion and mutagenesis analysis revealed that the -131/ +19 region, co ntaining two Pit-1 sites, or four copies of the most proximal site tiGHF1 f used to the heterologous Tk promoter, confer high level expression in rat p ituitary cells and direct transcription in non-pituitary cells only after e xpression of rat Pit-1. We show that a tilapia pituitary factor specificall y binds to site tiGHF1 and obtained a partial cDNA sequence coding for tila pia Pit-1. The cAMP stimulation is mediated by the proximal (-131/-31) prom oter region. It is Pit-1-dependent and requires the tiCHF1 site. In additio n, four copies of this site confer cAMP inducibility to the Tk promoter in GC cells. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights re served.