title: Oct-3/4 and Sox2 regulate Oct-3/4 gene in embryonic stem cells.
abstract: Oct-3/4 is a key transcriptional factor whose expression level governs the fate of primitive inner cell mass and embryonic stem (ES) cells. Previously, an upstream 3.3-kb distal enhancer (DE) fragment was identified to be responsible for the specific expression of mouse Oct-3/4 in the inner cell mass and ES cells. However, little is known about the cis-elements and trans-factors required for DE activity. In this study, we identified a novel cis-element, called Site 2B here, located approximately 30 bp downstream from Site 2A, which was previously revealed in DE by an in vivo chemical modification experiment. Using the luciferase reporter assay, we demonstrated that both Site 2A and Site 2B are necessary and sufficient for activating DE in the contexts of both the native Oct-3/4 promoter and the heterologous thymidine kinase minimal promoter. In an electrophoretic mobility shift assay we showed that Site 2B specifically binds to Oct-3/4 and Sox2 when ES-derived cell extracts were used, whereas Site 2A binds to a factor(s) present in both ES and NIH 3T3 cells. Furthermore, we showed that the physiological level of Oct-3/4 in ES cells is required for Site 2B-mediated DE activity using the inducible knock-out system of Oct-3/4 in ES cells. These results indicate that Oct-3/4 is a member of the gene family regulated by Oct-3/4 and Sox2, as reported before for the FGF-4, UTF1, Sox2, and Fbx15 genes. Thus, Oct-3/4 and Sox2 comprise a regulatory complex that controls the expression of genes important for the maintenance of the primitive state, including themselves. This autoregulatory circuit of the Sox2.Oct-3/4 complex may contribute to maintaining robustly the precise expression level of Oct-3/4 in primitive cells.
authors.affiliation: Laboratory of Molecular and Cellular Assembly, Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatuda, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Okumura-Nakanishi
authors.forename: Motoki
authors.initials: M
authors.lastname: Saito
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Niwa
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Ishikawa
mesh_terms: D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004622:Embryo, Mammalian / Q000166:cytology*; D004742:Enhancer Elements, Genetic / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D050814:Octamer Transcription Factor-3; D011401:Promoter Regions, Genetic / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D055748:SOXB1 Transcription Factors; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; C494174:Pou5f1 protein, mouse; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D014212:Tretinoin