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Dominant role of DNA methylation over H3K9me3 in ERV silencing during embryonic endoderm development [RNA-Seq Suv39]

ABSTRACT: Silencing of endogenous retroviruses (ERVs) is largely mediated by repressive chromatin modifications, such as H3K9me3 and DNA methylation. Their impact on ERV silencing differs in various cell types and, no systematic analyses on the interdependence between H3K9me3 and DNA methylation have been performed in differentiated cells. Here we show that deletion of the H3K9me3 HMTase Setdb1 in mouse embryonic endoderm results in ERV de-repression in only a subset of endoderm cells. We found that de-repression is restricted to visceral endoderm descendants and does not occur in definitive endoderm cells. Deletion of Setdb1 in visceral endoderm progenitors resulted in loss of H3K9me3 and reduced DNA methylation of IAPEz, consistent with up-regulation of this ERV family. In definitive endoderm cells, loss of Setdb1 did not affect H3K9me3 nor DNA methylation, suggesting Setdb1-independent pathways for maintaining these modifications. Importantly, Dnmt1 ko resulted in ERV de-repression in both visceral and definitive endoderm cells, while H3K9me3 was unaltered. Thus, our data suggest a dominant role of DNA methylation over H3K9me3 in ERV silencing in endoderm cells. Our findings suggest, that H3K9me3 is not sufficient for ERV silencing, but rather critical for maintaining high DNA methylation.

ORGANISM(S): Mus musculus

PROVIDER: GSE169462 | GEO | 2022/08/01

REPOSITORIES: GEO

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Project description:Endogenous retroviruses (ERVs) comprise a significant portion of mammalian genomes. Although specific ERV loci feature regulatory roles for host gene expression, most ERV integrations are transcriptionally repressed by Setdb1 mediated H3K9me3 and DNA methylation. However, the protein network which regulates the deposition of these chromatin modifications is still incompletely understood. Here, we performed a genome-wide sgRNA screen for genes involved in ERV silencing and identified the GHKL ATPase protein Morc3 as a top-scoring hit. Morc3 knock-out cells display de-repression, reduced H3K9me3, and increased chromatin accessibility of distinct ERV families. We found that the Morc3 ATPase cycle and Morc3 SUMOylation are important for ERV chromatin regulation. Proteomic analysis revealed that Morc3 mutant proteins fail to interact with the histone H3.3 chaperone Daxx. This interaction depends on Morc3 SUMOylation and Daxx SUMO binding. Notably, in Morc3 ko cells, we observed strongly reduced histone H3.3 on Morc3 binding sites. Thus, our data demonstrate Morc3 as a critical regulator of Daxx-mediated histone H3.3 incorporation to ERV regions. This dataset comprises several experiments addressing different questions: 1. ChIP-MS experiment to determine the protein interaction context of Morc3 using a Morc3-3xFLAG knock-in ES cell line compared to wild type ES cells (Experiment 20200408). 2. ChIP-MS experiments to investigate changes in the protein interaction context of the Morc3 mutant rescue cell lines. Comparison of Morc3 knock-out cell lines with re-expression of Morc3-CW-3xFLAG mutant (Ref. #3111), Morc3-ATP-binding-3xFLAG and Morc3-SUMOylation-3xFLAG mutants (Ref. #3635), and Morc3-deltaN-3xFLAG mutant (Ref. #5174) compared to wt Morc3-3XFLAG rescue. 3. ChIP-MS experiment to determine if the interaction between Morc3 and Daxx is mediated through this C-terminal SIM, comparing Daxx knock-out cell lines with re-expression of wild type 3xFLAG-Daxx protein or 3xFLAG-Daxx ∆SIM, which lacks the C-terminal SIM domain. (Ref. #3301)

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Dominant role of DNA methylation over H3K9me3 in ERV silencing during embryonic endoderm development [RNA-Seq Suv39]

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