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Uhrf1 regulates active transcriptional marks at bivalent domains in pluripotent stem cells through Setd1a [RNA-Seq]

ABSTRACT: Embryonic stem cells (ESCs) maintain pluripotency through unique epigenetic states. When ESCs commit to a specific cell lineage, changes in histone modifications and DNA methylation accompany the transition to more specialized cell types. Investigating how epigenetic regulation maintains pluripotency is a critical component in order to generate the required cell types for future clinical application. Uhrf1 is a widely known hemi-methylated DNA binding protein, playing a role in heterochromatin formation alongside G9a, Trim28 and HDACs. In addition, it has been demonstrated that Uhrf1 functions to maintain DNA methylation through the recruitment of Dnmt1. Although Uhrf1 is not essential in ESC self-renewal, it still remains elusive how Uhrf1 regulates pluripotency. Here, we set out to elucidate the role of Uhrf1 in pluripotent stem cells. We found that Uhrf1 forms a complex with the active trithorax group of transcriptional regulators, in particular the Setd1a/COMPASS complex. Our data show that loss of Uhrf1 causes a dramatic reduction of bivalent histone marks, in particular those associated with neuroectoderm and mesoderm specification. Overall, our data demonstrate that Uhrf1 safeguards the balance between pluripotency and differentiation via the Setd1a/COMPASSS complex, through which Uhrf1 mediates bivalent histone modifications.

ORGANISM(S): Mus musculus

PROVIDER: GSE113914 | GEO | 2018/05/02

REPOSITORIES: GEO

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Project description:Epigenetic priming factors establish a permissive epigenetic landscape which is not required until a later developmental or physiological time point, temporally uncoupling the presence of these factors with their phenotypic effects. One classic example of epigenetic priming is in the context of bivalent chromatin, found in pluripotent stem cells and early embryos at key developmental gene promoters marked by both activating-associated H3K4me3 and repressive-associated H3K27me3 histone modifications. It is currently unknown how these bivalent domains are targeted, or precisely how they impact on lineage commitment. Here we show that the small heterodimerising non-enzymatic DNA binding proteins Developmental Pluripotency Associated 2 (Dppa2) and 4 (Dppa4) act as epigenetic priming factors to establish bivalency at a subset of developmental genes. Dppa2/4 localise to the +1 nucleosome position of bivalent genes and while they are not required for pluripotency in embryonic stem cells (ESCs), double knockout cells fail to exit pluripotency and to differentiate efficiently, with delays in upregulating bivalently marked lineage genes. Proteomics reveal that Dppa2/4 interact on chromatin with members of the COMPASS and Polycomb complexes important for H3K4me3 and H3K27me3 deposition, respectively. Epigenetic profiling reveals a striking loss of H3K4me3, H3K27me3, and their associated enzymatic machinery at a significant subset of bivalent promoters in Dppa2/4 mutants, in addition to loss of H2A.Z and chromatin accessibility. In wild-type ESCs, these “Dppa2/4-dependent” bivalent promoters are characterised by low H3K4me3 enrichment and breadth, near-absent expression levels and initiating but not elongating RNA polymerase. Notably, Dppa2/4-dependent promoters are less evolutionarily conserved suggesting that they lack additional safeguard measures to maintain bivalency at these genes in the absence of Dppa2/4. Concomitantly with the loss of bivalency, Dppa2/4-dependent bivalent promoters gain DNA methylation and consequently are no longer able to be effectively activated upon ESC differentiation, leading to defects in cell fate acquisition. Our findings reveal a targeting principle for bivalency to developmental gene promoters poising them for future lineage specific gene activation.

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Uhrf1 regulates active transcriptional marks at bivalent domains in pluripotent stem cells through Setd1a [RNA-Seq]

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