Differential expression of AP-2 gamma and AP-2 alpha during human trophoblast differentiation

Previous studies from our laboratory demonstrated that AP-2 alpha induces t he expression of the hPL and hCG genes in cultured trophoblast cells. In th e current study, we have shown by transient transfection studies that AP-2 gamma, which is the product of a separate gene from AP-2 alpha, also stimul ates hPL and hCG beta promoter activities. However, AP-2 gamma mRNA levels during in vitro differentiation of human cytotrophoblast cells were strikin gly different than those of AP-2 alpha mRNA levels, with AP-2 gamma increas ing and AP-2 gamma markedly decreasing during the differentiation process. The amount of AP-2 gamma protein binding to AP-2 elements on the hPL promot er, as determined by supershift assays, also markedly decreased during the differentiation process. These findings strongly suggest that AP-2 gamma ac tion in cytotrophoblast cells is repressed by a co-factor(s) that inhibits AP-2 gamma action or is prevented by the absence of a co-factor(s) that is essential for AP-2 gamma action. (C) 2001 Elsevier Science Inc. All rights reserved.