Figure 3.

CBP and Pit-1 synergistic activation of the hGH promoter after GHRH stimulation does not require the presence of CREs. CV-1 cells were transfected with hGHRH receptor and SV-40 expression vectors (pSG5) containing either Pit-1 or CBP cDNAs in the presence of (a) 195 bp of the hGH promoter (b) mutation of the pCRE, or (c) deletion of an additional 55 bp of the hGH promoter, with loss of the dCRE. Stimulation was with hGHRH(1-29)-NH₂ for 6 hours, or with BSA as a control. Data are expressed as mean fold activation ± SEM relative to EV Pit-1 plus EV CBP after stimulation with BSA. Significant activation was not seen without cotransfection of the GHRH receptor (data not shown).