Abstract
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.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Binding Sites / drug effects
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Binding Sites / genetics
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Binding, Competitive / drug effects
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Cattle
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Choriocarcinoma / metabolism
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DNA-Binding Proteins / biosynthesis
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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DNA-Binding Proteins / pharmacology
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Enhancer Elements, Genetic / physiology
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Gene Silencing / drug effects
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Gene Silencing / physiology
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Genes, Reporter / drug effects
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Genes, Reporter / physiology
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Host Cell Factor C1
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Humans
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Interferon Type I / genetics*
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Interferon Type I / metabolism
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Macromolecular Substances
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Mutagenesis, Site-Directed
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Octamer Transcription Factor-1
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Octamer Transcription Factor-2
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Octamer Transcription Factor-3
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Precipitin Tests
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Pregnancy Proteins / genetics*
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Pregnancy Proteins / metabolism
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Promoter Regions, Genetic / drug effects
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Promoter Regions, Genetic / genetics*
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Protein Structure, Tertiary / physiology
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Proto-Oncogene Protein c-ets-2
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins / pharmacology
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Repressor Proteins*
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Substrate Specificity / genetics
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Trans-Activators / genetics
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Trans-Activators / metabolism*
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Trans-Activators / pharmacology
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Transcription Factors / biosynthesis
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transcription Factors / pharmacology
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Transcriptional Activation / drug effects
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Transcriptional Activation / physiology*
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Transfection
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Tumor Cells, Cultured
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Up-Regulation / drug effects
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Up-Regulation / physiology
Substances
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DNA-Binding Proteins
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ERF protein, human
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ETS2 protein, human
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HCFC1 protein, human
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Host Cell Factor C1
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Interferon Type I
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Macromolecular Substances
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Octamer Transcription Factor-1
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Octamer Transcription Factor-2
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Octamer Transcription Factor-3
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POU2F1 protein, human
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POU2F2 protein, human
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POU5F1 protein, human
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Pregnancy Proteins
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Proto-Oncogene Protein c-ets-2
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Proto-Oncogene Proteins
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Repressor Proteins
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Trans-Activators
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Transcription Factors
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interferon tau