Unknown,Transcriptomics,Genomics,Proteomics

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Genome-wide distribution of 5-formylcytosine in ES cells is associated with transcription and depends on TDG

ABSTRACT: Methylation of cytosine in DNA (5mC) is an important epigenetic mark that is involved in the regulation of genome function. During early embryonic development in mammals, the DNA methylation landscape is dynamically reprogrammed in part through active demethylation. Recent advances have identified key players involved in active demethylation pathways, including oxidation of 5mC to 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) by the TET family of enzymes and excision of 5fC by the base excision repair enzyme thymine DNA glycosylase (TDG). Here, we provide the first genome-wide distribution map of 5fC in mouse embryonic stem (ES) cells and evaluate potential roles for 5fC in differentiation. Our method exploits the unique reactivity of 5fC to link a biotin tag for pulldown and high-throughput sequencing. Genome-wide mapping revealed 5fC enrichment in CpG islands (CGIs) of promoters and exons. CGI promoters in which 5fC was relatively more enriched than 5mC or 5hmC corresponded to transcriptionally active genes. Accordingly, 5fC-rich promoters had elevated H3K4me3 levels, a histone mark associated with active transcription, and were frequently bound by RNA Polymerase II. Downregulation of TDG led to accumulation of 5fC in CGIs in ES cells, which correlates with increased methylation in these genomic regions during differentiation and in mouse embryonic fibroblasts derived from TDG knockout embryos. Collectively, our data suggest that 5fC plays a role in epigenetic reprogramming. The formation and removal of this cytosine modification are confined to specific genomic regions, which are in part controlled by TDG. Notably, 5fC excision in ES cells is necessary for the correct establishment of CGI methylation patterns during differentiation, and hence, for appropriate patterns of gene expression during development. We devised a method to map 5-formylcytosine (5fC) by linking a biotin tag to 5fC for pulldown and high-throughput sequencing. We mapped 5fC in the following samples of mouse embryonic stem cells (J1): Wild-type ES cells (two replicates); ES cells transfected with siRNA targeting TDG (two replicates); ES cells transfected with non-targeting siRNA (two replicates). One genomic input library was also sequenced to detect and correct biases in fragment enrichment.

ORGANISM(S): Mus musculus

SUBMITTER: Dario Beraldi

PROVIDER: E-GEOD-40148 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Genome-wide distribution of 5-formylcytosine in embryonic stem cells is associated with transcription and depends on thymine DNA glycosylase.

Raiber Eun-Ang EA Beraldi Dario D Ficz Gabriella G Burgess Heather E HE Branco Miguel R MR Murat Pierre P Oxley David D Booth Michael J MJ Reik Wolf W Balasubramanian Shankar S

Genome biology 20120817 8

<h4>Background</h4>Methylation of cytosine in DNA (5mC) is an important epigenetic mark that is involved in the regulation of genome function. During early embryonic development in mammals, the methylation landscape is dynamically reprogrammed in part through active demethylation. Recent advances have identified key players involved in active demethylation pathways, including oxidation of 5mC to 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) by the TET enzymes, and excision of 5fC by ...[more]

PMID: 22902005

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Project description:TET proteins oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). 5fC and 5caC are excised by mammalian DNA glycosylase TDG, implicating 5mC oxidation in DNA demethylation. Here we show that the genomic locations of 5fC can be determined by coupling chemical reduction with biotin tagging. Genome-wide mapping of 5fC in mouse embryonic stem cells (mESCs) reveals that 5fC preferentially occurs at poised enhancers among other gene regulatory elements. Application to Tdg null mESCs further suggests that 5fC production coordinates with p300 in remodeling epigenetic states of enhancers. This process, which is not influenced by 5hmC, appears to be associated with further oxidation of 5hmC and commitment to demethylation through 5fC. Finally, we resolved 5fC at base-resolution by hydroxylamine-based protection from bisulfite-mediated deamination, thereby confirming sites of 5fC accumulation. Our results reveal roles of active 5mC/5hmC oxidation and TDG-mediated demethylation in epigenetic tuning at regulatory elements. We report here a chemical labeling method that effectively differentiates 5fC from 5mC, 5hmC, and 5caC in genomic DNA. First, we quantitatively protect endogenous 5hmC with a regular glucose using b-glucosytransferase-catalyzed 5hmC glucosylation. Then, we selectively reduce 5fC with NaBH4 to 5hmC, and chemically label the resulting 5hmC (from 5fC) with an azide-modified glucose. Biotin can be installed subsequently for specific enrichment of 5fC. Our method thereby provides an effective tool of general utility for the genomic localization of 5fC. Here we provide genome-wide profiles of 5hmC, 5fC, and p300 in Tdg fl/fl and Tdg-/- mESCs as well as a 5fC control (Non-NaBH4) and polyA RNA-Seq expression data. Genome-wide profiles of 5hmC and 5fC in mESCs differentiated to embryoid bodies are also included. We also report the development and application of a single-base resolution method for the detection of 5fC in genomic DNA by hydroylamine mediated protection of 5fC from deamination during bisulfite treatment, or 5fC Chemical Assisted Bisulfite Sequencing (fCAB-Seq). We applied this method in parallel with conventional ChIP-Methyl-Seq to H3K4me1 ChIP enriched DNA from Tdg fl/fl and Tdg-/- mice.

Project description:Background: Genome-wide methylation of cytosine can be modulated in the presence of TET and thymine DNA glycosylase (TDG) enzymes. TET enzymes are able to oxidise 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). TDG can excise the oxidative products 5fC and 5caC, initiating base excision repair. Furthermore, these modified bases are stable and detectable in the genome, raising the possibility that they could have epigenetic functions in their own right. To date, functional investigation of the genome-wide distribution of 5fC has been restricted to cell culture based systems, while its in vivo profile, in particular during development, remains unknown. Results: Here we describe the first analysis of the in vivo genome-wide profile of 5fC, across a range of dissected tissues from both wild type and Tdg-deficient E11.5 mouse embryos. Changes in the formylation profile of cytosine upon depletion of TDG suggest TET/TDG-mediated active demethylation occurs preferentially at intron-exon boundaries, and reveals a major role for TDG in shaping 5fC distribution at CpG islands. Moreover, we find enhancer regions exhibit high levels of 5fC, which accumulates at tissue-specific enhancers implicating a role in embryonic development. Conclusions: The tissue-specific distribution of 5fC can be regulated by the collective contribution of TET-mediated oxidation and excision by TDG. We show that the in vivo profile of 5fC during embryonic development resembles that of embryonic stem cells, sharing key features including enrichment of 5fC in enhancer and intragenic regions. Additionally, by investigating 5fC profiles in a tissue-specific manner from mouse embryos, we identified a targeted enrichment at active enhancers involved in tissue development. 5-formylcytosine has been mapped genomewide by pull-down and sequencing in mouse hindbrain, heart, carcass and liver. Each tissue was replicated in two different mice except for hindbrain which was replicated in four different mice.

Dataset Information

Genome-wide distribution of 5-formylcytosine in ES cells is associated with transcription and depends on TDG

Publications

Genome-wide distribution of 5-formylcytosine in embryonic stem cells is associated with transcription and depends on thymine DNA glycosylase.

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