Role of chicken Pit-1 isoforms in activating growth hormone gene

In the present study, we expressed chicken (ch) Pit-1α (chPit-1α) and chPit-1γ in vitro to compare the roles of chPit-1s in the transcription of the chicken growth hormone (chGH) gene. Both green fluorescence protein (GFP)-fused chPit-1γ and GFP-fused chPit-1α were localized in the nuclei of COS-7 cells. In a luciferase reporter gene assay, both chPit-1α and chPit-1γ transactivated the chGH promoter, and chPit-1α showed a more potent effect than chPit-1γ. On the other hand, an increase of cellular cAMP induced by forskolin promoted transactivation of the chGH gene with chPit-1α and chPit-1γ to similar extents. These results suggest that chPit-1γ may modulate the basal promoter activity of the chGH gene to the same degree as chPit-1α; however, a structural difference observed at the N-terminus transactivation domains in chPit-1α and chPit-1γ could be associated with the efficiency of basal activation of the chGH promoter.

► Chicken Pit-1α and Pit-1γ localized in the nuclei in COS-7 cells.
► Chicken Pit-1α and Pit-1γ induced transactivation of chicken GH gene, but Pit-1α was a more potent isoform in the activation of chicken GH gene.
► Forskolin promoted induction of chGH gene with chicken Pit-1α and Pit-1γ at similar extent.