Abstract
Expression of the tilapia growth hormone (tiGH) gene is pituitary-specific and controlled by intracellular cAMP levels. DNaseI protection experiments allowed us to identify four Pit-1 binding sites in the tiGH −465/+19 region. Deletion and mutagenesis analysis revealed that the −131/+19 region, containing two Pit-1 sites, or four copies of the most proximal site tiGHF1 fused to the heterologous Tk promoter, confer high level expression in rat pituitary cells and direct transcription in non-pituitary cells only after expression of rat Pit-1. We show that a tilapia pituitary factor specifically binds to site tiGHF1 and obtained a partial cDNA sequence coding for tilapia Pit-1. The cAMP stimulation is mediated by the proximal (−131/−31) promoter region. It is Pit-1-dependent and requires the tiGHF1 site. In addition, four copies of this site confer cAMP inducibility to the Tk promoter in GC cells.
Published Version
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