During embryogenesis, many key transcription factors are used repeatedly, achieving different outcomes depending on cell type and developmental stage. The epigenetic modification of the genome functions as a memory of a cells developmental history, and it has been proposed that such modification shapes the cellular response to transcription factors. To investigate the role of DNA methylation in the response to transcription factor Gata4, we examined expression profiles of Dnmt3a-/-Dnmt3b-/- ES cell-derived mesoderm cells cultured for 4 days with or without Gata4 activation, as well as the wild-type counterparts, using Affymetrix microarrays.
DNA methylation restricts lineage-specific functions of transcription factor Gata4 during embryonic stem cell differentiation.
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View SamplesWe examined the transcriptional function of cyclin D1 in mouse development using two approaches. First, we queried association of cyclin D1 with the genome of E14.5 mouse embryos using ChIP-on-chip approach. We observed binding of cyclin D1 to several promoter regions. Second, we compared gene expression profiles between wild-type and cyclin D1-null retinas. We observed several transcripts with altered levels in cyclin D1-null organs.
Transcriptional role of cyclin D1 in development revealed by a genetic-proteomic screen.
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View SamplesCyclin D1 belongs to the core cell cycle machinery1, and it is frequently overexpressed in human cancers2. The full repertoire of cyclin D1 functions in normal development and in cancer cells is currently unknown. To address this question, here we introduce a novel approach that allows one to determine the set of cyclin D1-interacting proteins (D1 interactome) and cyclin D1-bound genomic fragments (D1 cistrome) in essentially any mouse organ, at any point of development or at any stage of cancer progression. Using this approach, we detected several novel tissue-specific interactors of cyclin D1. A significant number of these partners represent proteins involved in transcription. We show, using genome-wide location analysis3, that cyclin D1 occupies promoters of a very large number of genes in the developing mouse, where it binds in close proximity to transcription start sites. Bioinformatics analyses of cyclin D1-bound genomic segments in the developing embryo revealed DNA recognition sequences for several transcription factors. By querying SAGE libraries4, promoter CpG content5 and gene expression profiles of cyclin D1-null organs, we demonstrate that cyclin D1 binds promoters of highly expressed genes, and that it functions to activate or to repress gene expression in vivo. Analyses of cyclin D1 transcriptional targets reveal that cyclin D1 contributes to cell proliferation by upregulating genes required for S-phase entry and progression. Hence, cyclin D1 plays a broad transcriptional regulatory function in vivo during normal mouse development.
Transcriptional role of cyclin D1 in development revealed by a genetic-proteomic screen.
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