Silencing of the gene for the beta subunit of human chorionic gonadotropin by the embryonic transcription factor Oct-3/4

J Biol Chem. 1996 Jul 12;271(28):16683-9. doi: 10.1074/jbc.271.28.16683.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Sequence
  • Binding Sites
  • Choriocarcinoma / genetics
  • Choriocarcinoma / pathology
  • Chorionic Gonadotropin / biosynthesis
  • Chorionic Gonadotropin, beta Subunit, Human / genetics*
  • DNA, Complementary
  • DNA-Binding Proteins / metabolism*
  • Embryo, Mammalian / metabolism*
  • Female
  • Gene Expression Regulation, Developmental
  • Humans
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Octamer Transcription Factor-3
  • Pregnancy
  • Promoter Regions, Genetic
  • Transcription Factors / metabolism*
  • Transfection
  • Tumor Cells, Cultured

Substances

  • Chorionic Gonadotropin
  • Chorionic Gonadotropin, beta Subunit, Human
  • DNA, Complementary
  • DNA-Binding Proteins
  • Octamer Transcription Factor-3
  • POU5F1 protein, human
  • Transcription Factors