Silencing of the gene for the beta subunit of human chorionic gonadotropin by the embryonic transcription factor Oct-3/4.
The transcription factor Oct-3/4 may be important in maintaining embryonic cells in an undifferentiated state. It is probably down-regulated at about the time that human chorionic gonadotropin (hCG) is first expressed in embryonic trophectoderm. Here we report that Oct-3/4 strongly inhibits the hCGbeta subunit (hCGbeta) promoter in JAr choriocarcinoma cells. Oct-3/4 reduced chloramphenicol acetyltransferase (CAT) reporter expression from the -305hCGbeta promoter by about 90% in transient co-transfection assays, but had no effect on expression from the -249hCGbeta promoter. The -305/-249 hCGbeta fragment specifically bound synthetic Oct-3/4 protein as measured in electrophoretic mobility shift assays, and the Oct-3/4-binding site was localized around -270 by methylation interference footprinting. Site-directed mutagenesis of this binding site abolished Oct-3/4 repression. When stably transfected into JAr cells, Oct-3/4 reduced the amounts of both endogenous hCGbeta messenger RNA and hCG protein to less than 10% of controls. We suggest that silencing of Oct-3/4 in trophectoderm is a prerequisite for hCG up-regulation in early human embryos at the time of maternal recognition of pregnancy.
Liu
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Department of Biological Sciences, University of Missouri, Columbia, Missouri 65211, USA.
Roberts
R M
RM
D001483:Base Sequence; D001665:Binding Sites; D002822:Choriocarcinoma / Q000235:genetics / Q000473:pathology; D006063:Chorionic Gonadotropin / Q000096:biosynthesis; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000235:genetics*; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050814:Octamer Transcription Factor-3; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D014157:Transcription Factors