| 1. |
- Nestor, Colm E, et al.
(författare)
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Investigating 5-hydroxymethylcytosine (5hmC) : the state of the art
- 2014
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Ingår i: Methods in Molecular Biology. - Totowa, NJ : Humana Press. - 1064-3745 .- 1940-6029. ; 1094, s. 243-58
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of 5-hydroxymethylcytosine (5hmC) as an abundant base in mammalian genomes has excited the field of epigenetics, and stimulated an intense period of research activity aimed at decoding its biological significance. However, initial research efforts were hampered by a lack of assays capable of specifically detecting 5hmC. Consequently, the last 3 years have seen the development of a plethora of new techniques designed to detect both global levels and locus-specific profiles of 5hmC in mammalian genomes. This research effort has culminated in the recent publication of two complementary techniques for quantitative, base-resolution mapping of 5hmC in mammalian genomes, the first true mammalian hydroxymethylomes. Here, we review the techniques currently available to researchers studying 5hmC, discuss their advantages and disadvantages, and explore the technical hurdles which remain to be overcome.
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| 2. |
- Reddington, James P, et al.
(författare)
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Redistribution of H3K27me3 upon DNA hypomethylation results in de-repression of Polycomb target genes
- 2013
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Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 14:3, s. R25-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: DNA methylation and the Polycomb repression system are epigenetic mechanisms that play important roles in maintaining transcriptional repression. Recent evidence suggests that DNA methylation can attenuate the binding of Polycomb protein components to chromatin and thus plays a role in determining their genomic targeting. However, whether this role of DNA methylation is important in the context of transcriptional regulation is unclear.RESULTS: By genome-wide mapping of the Polycomb Repressive Complex 2-signature histone mark, H3K27me3, in severely DNA hypomethylated mouse somatic cells, we show that hypomethylation leads to widespread H3K27me3 redistribution, in a manner that reflects the local DNA methylation status in wild-type cells. Unexpectedly, we observe striking loss of H3K27me3 and Polycomb Repressive Complex 2 from Polycomb target gene promoters in DNA hypomethylated cells, including Hox gene clusters. Importantly, we show that many of these genes become ectopically expressed in DNA hypomethylated cells, consistent with loss of Polycomb-mediated repression.CONCLUSIONS: An intact DNA methylome is required for appropriate Polycomb-mediated gene repression by constraining Polycomb Repressive Complex 2 targeting. These observations identify a previously unappreciated role for DNA methylation in gene regulation and therefore influence our understanding of how this epigenetic mechanism contributes to normal development and disease.
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| 3. |
- Hackett, Jamie A., et al.
(författare)
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Promoter DNA methylation couples genome-defence mechanisms to epigenetic reprogramming in the mouse germline
- 2012
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 139:19, s. 3623-3632
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Tidskriftsartikel (refereegranskat)abstract
- Mouse primordial germ cells (PGCs) erase global DNA methylation (5mC) as part of the comprehensive epigenetic reprogramming that occurs during PGC development. 5mC plays an important role in maintaining stable gene silencing and repression of transposable elements (TE) but it is not clear how the extensive loss of DNA methylation impacts on gene expression and TE repression in developing PGCs. Using a novel epigenetic disruption and recovery screen and genetic analyses, we identified a core set of germline-specific genes that are dependent exclusively on promoter DNA methylation for initiation and maintenance of developmental silencing. These gene promoters appear to possess a specialised chromatin environment that does not acquire any of the repressive H3K27me3, H3K9me2, H3K9me3 or H4K20me3 histone modifications when silenced by DNA methylation. Intriguingly, this methylation-dependent subset is highly enriched in genes with roles in suppressing TE activity in germ cells. We show that the mechanism for developmental regulation of the germline genome-defence genes involves DNMT3B-dependent de novo DNA methylation. These genes are then activated by lineage-specific promoter demethylation during distinct global epigenetic reprogramming events in migratory (~E8.5) and post-migratory (E10.5-11.5) PGCs. We propose that genes involved in genome defence are developmentally regulated primarily by promoter DNA methylation as a sensory mechanism that is coupled to the potential for TE activation during global 5mC erasure, thereby acting as a failsafe to ensure TE suppression and maintain genomic integrity in the germline.
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