title: The expression of the human chorionic gonadotropin beta subunit gene depends on negative control.
abstract: Transcription of the human chorionic gonadotropin (hCG) genes begins in the very early embryo stage and decreases or even disappears in nonplacental tissues. We have studied the regulation of hCG-beta genes by cell fusion and by the reverse transcription-polymerase chain reaction (RT-PCR). The choriocarcinoma cell lines, JAR and JEG-3, express high levels of the hCG-beta subunit while HeLa cells express extremely low levels of it. Most HeLa x JAR and HeLa x JEG-3 fusion clones expressed only a trace of the hCG-beta subunit mRNA, while JAR x JEG-3 fusion clones still expressed high levels of the hCG-beta subunit. Most transcripts of the hCG-beta subunit genes in JAR and JEG-3 came from the hCG-beta 5 subunit. Even the trace amount of hCG-beta transcripts from fusion clones came mainly from the beta-5 gene. The results suggest that the expression of the hCG-beta subunit genes depends on negative control. Probably when embryonic cells differentiate to form nonplacental tissues, specific inhibitors may appear and inhibit the expression of the hCG-beta subunit genes.
authors.affiliation: Department of Pharmacy, College of Medicine, National Taiwan University Hospital, National Taiwan University, Taipei.
authors.forename: Y H
authors.initials: YH
authors.lastname: Chen
authors.forename: T M
authors.initials: TM
authors.lastname: Chen
authors.forename: C Y
authors.initials: CY
authors.lastname: Hsieh
mesh_terms: D002459:Cell Fusion; D006063:Chorionic Gonadotropin / Q000235:genetics*; D004247:DNA / Q000032:analysis; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D016133:Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: D006063:Chorionic Gonadotropin; D004247:DNA