Repression of Ets-2-induced transactivation of the tau interferon promoter by Oct-4.
Oct-4 is a POU family transcription factor associated with potentially totipotent cells. Genes expressed in the trophectoderm but not in embryos prior to blastocyst formation may be targets for silencing by Oct-4. Here, we have tested this hypothesis with the tau interferon genes (IFNT genes), which are expressed exclusively in the trophectoderm of bovine embryos. IFNT promoters contain an Ets-2 enhancer, located at -79 to -70, and are up-regulated about 20-fold by the overexpression of Ets-2 in human JAr choriocarcinoma cells, which are permissive for IFNT expression. This enhancement was reversed in a dose-dependent manner by coexpression of Oct-4 but not either Oct-1 or Oct-2. When cells were transfected with truncated bovine IFNT promoters designed to eliminate potential octamer sites sequentially, luciferase reporter expression from each construct was still silenced by Oct-4. Full repression required both the N-terminal and POU domains of Oct-4, but neither domain used alone was an effective silencer. Oct-4 and Ets-2 formed a complex in vitro in the absence of DNA through binding of the POU domain of Oct-4 to a site located between the "pointed" and DNA binding domains of Ets-2. The two transcription factors were also coimmunoprecipitated after being expressed together in JAr cells. Oct-4, therefore, silences IFNT promoters by quenching Ets-2 transactivation. The POU domain most probably binds to Ets-2 directly, while the N-terminal domain inhibits transcription. These findings provide further evidence that the developmental switch to the trophectoderm is accompanied by the loss of Oct-4 silencing of key genes.
Ezashi
T
T
Department of Animal Sciences and Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
Ghosh
D
D
Roberts
R M
RM
D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D001667:Binding, Competitive / Q000187:drug effects; D002417:Cattle; D002822:Choriocarcinoma / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D004742:Enhancer Elements, Genetic / Q000502:physiology; D020868:Gene Silencing / Q000187:drug effects / Q000502:physiology; D017930:Genes, Reporter / Q000187:drug effects / Q000502:physiology; D051863:Host Cell Factor C1; D006801:Humans; D007370:Interferon Type I / Q000235:genetics* / Q000378:metabolism; D046911:Macromolecular Substances; D016297:Mutagenesis, Site-Directed; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D050814:Octamer Transcription Factor-3; D011233:Precipitin Tests; D011257:Pregnancy Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics*; D017434:Protein Structure, Tertiary / Q000502:physiology; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D012097:Repressor Proteins; D013379:Substrate Specificity / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D004268:DNA-Binding Proteins; C107465:ERF protein, human; C494069:ETS2 protein, human; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D007370:Interferon Type I; D046911:Macromolecular Substances; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D050814:Octamer Transcription Factor-3; C494165:POU2F1 protein, human; C058435:POU2F2 protein, human; C494173:POU5F1 protein, human; D011257:Pregnancy Proteins; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C020947:interferon tau