title: Squelching of ETS2 transactivation by POU5F1 silences the human chorionic gonadotropin CGA subunit gene in human choriocarcinoma and embryonic stem cells.
abstract: The subunit genes encoding human chorionic gonadotropin, CGA, and CGB, are up-regulated in human trophoblast. However, they are effectively silenced in choriocarcinoma cells by ectopically expressed POU domain class 5 transcription factor 1 (POU5F1). Here we show that POU5F1 represses activity of the CGA promoter through its interactions with ETS2, a transcription factor required for both placental development and human chorionic gonadotropin subunit gene expression, by forming a complex that precludes ETS2 from interacting with the CGA promoter. Mutation of a POU5F1 binding site proximal to the ETS2 binding site does not alter the ability of POU5F1 to act as a repressor but causes a drop in basal promoter activity due to overlap with the binding site for DLX3. DLX3 has only a modest ability to raise basal CGA promoter activity, but its coexpression with ETS2 can up-regulate it 100-fold or more. The two factors form a complex, and both must bind to the promoter for the combination to be transcriptionally effective, a synergy compromised by POU5F1. Similarly, in human embryonic stem cells, which express ETS2 but not CGA, ETS2 does not occupy its binding site on the CGA promoter but is found instead as a soluble complex with POU5F1. When human embryonic stem cells differentiate in response to bone morphogenetic protein-4 and concentrations of POU5F1 fall and hCG and DLX3 rise, ETS2 then occupies its binding site on the CGA promoter. Hence, a squelching mechanism underpins the transcriptional silencing of CGA by POU5F1 and could have general relevance to how pluripotency is maintained and how the trophoblast lineage emerges from pluripotent precursor cells.
authors.affiliation: Department of Veterinary Pathobiology, Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211, USA.
authors.forename: Rangan
authors.initials: R
authors.lastname: Gupta
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ezashi
authors.forename: R Michael
authors.initials: RM
authors.lastname: Roberts
mesh_terms: D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D002822:Choriocarcinoma / Q000378:metabolism*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D020868:Gene Silencing; D015292:Glycoprotein Hormones, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009154:Mutation; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D050787:Proto-Oncogene Protein c-ets-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014594:Uterine Neoplasms / Q000378:metabolism
chemical_list: C525809:BMP4 protein, human; D055415:Bone Morphogenetic Protein 4; C554042:CGA protein, human; D018997:Chorionic Gonadotropin, beta Subunit, Human; C088334:Distal-less homeobox proteins; C494069:ETS2 protein, human; D015292:Glycoprotein Hormones, alpha Subunit; D018398:Homeodomain Proteins; D009363:Neoplasm Proteins; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D050787:Proto-Oncogene Protein c-ets-2; D011994:Recombinant Proteins; D014157:Transcription Factors