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

Abstract

CG is required for maintenance of the corpus luteum during pregnancy in higher primates. As CG is a heterodimeric molecule, some form of coordinated control must be maintained over the transcription of its two subunit genes. We recently found that expression of human CG beta-subunit (hCGbeta) in JAr human choriocarcinoma cells was almost completely silenced by the embryonic transcription factor Oct-3/4, which bound to a unique ACAATAATCA octameric sequence in the hCGbeta gene promoter. Here we report that Oct-3/4 is also a potent inhibitor of hCG alpha-subunit (hCGalpha) expression in JAr cells. Oct-3/4 reduced human GH reporter expression from the -170 hCGalpha promoter in either the presence or absence of cAMP by about 70% in transient cotransfection assays, but had no effect on expression from either the -148 hCGalpha or the -99 hCGalpha promoter. Unexpectedly, no Oct-3/ 4-binding site was identified within the -170 to -148 region of the hCGalpha promoter, although one was found around position -115 by both methylation interference footprinting and electrophoretic mobility shift assays. Site-directed mutagenesis of this binding site destroyed the affinity of the promoter for Oct-3/4, but did not affect repression of the promoter. Therefore, inhibition of hCGalpha gene transcription by Oct-3/4 appears not to involve direct binding of this factor to the site responsible for silencing. When stably transfected into JAr cells, Oct-3/4 reduced the amounts of both endogenous hCGalpha mRNA and protein by 70-80%. Oct-3/4 is therefore capable of silencing both hCGalpha and hCGbeta gene expression. We suggest that as the trophoblast begins to form, reduction of Oct-3/4 expression permits the coordinated onset of transcription from the hCGalpha and hCGbeta genes.

• Authors: L Liu, D Leaman, M Villalta, R M Roberts
• Journal: Molecular endocrinology (Baltimore, Md.) (Mol Endocrinol) Vol. 11 Issue 11 Pg. 1651-8 (Oct 1997) ISSN: 0888-8809 [Print] United States
• PMID: 9328347 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Chorionic Gonadotropin, beta Subunit, Human
• DNA-Binding Proteins
• Fetal Proteins
• Glycoprotein Hormones, alpha Subunit
• HCFC1 protein, human
• Homeodomain Proteins
• Host Cell Factor C1
• Neoplasm Proteins
• Octamer Transcription Factor-1
• Octamer Transcription Factor-2
• Octamer Transcription Factor-3
• POU2F1 protein, human
• POU2F2 protein, human
• POU5F1 protein, human
• Repressor Proteins
• Transcription Factors

Topics

• Base Sequence
• Binding Sites
• Choriocarcinoma (pathology)
• Chorionic Gonadotropin, beta Subunit, Human (biosynthesis, genetics)
• Consensus Sequence
• DNA Footprinting
• DNA-Binding Proteins (pharmacology, physiology)
• Female
• Fetal Proteins (pharmacology)
• Gene Expression Regulation, Developmental (drug effects)
• Gene Expression Regulation, Neoplastic (drug effects)
• Glycoprotein Hormones, alpha Subunit (biosynthesis, genetics)
• Homeodomain Proteins (pharmacology, physiology)
• Host Cell Factor C1
• Humans
• Molecular Sequence Data
• Mutagenesis, Site-Directed
• Neoplasm Proteins (biosynthesis, genetics)
• Octamer Transcription Factor-1
• Octamer Transcription Factor-2
• Octamer Transcription Factor-3
• Promoter Regions, Genetic
• Regulatory Sequences, Nucleic Acid
• Repressor Proteins (genetics, physiology)
• Transcription Factors (pharmacology, physiology)
• Transfection
• Tumor Cells, Cultured (drug effects)
• Uterine Neoplasms (pathology)