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MBD4 loss results in global reactivation of promoters and retroelements with low methylated CpG density.

ABSTRACT: Inherited defects in the base-excision repair gene MBD4 predispose individuals to adenomatous polyposis and colorectal cancer, which is characterized by an accumulation of C>T transitions resulting from spontaneous deamination of 5’-methylcytosine. Despite its significance, this DNA repair pathway is still poorly understood. Here we show that the protein MBD4 is required for DNA methylation maintenance and G/T mismatch repair. Transcriptome and methylome analyses reveal a genome-wide hypomethylation of promoters, gene bodies and repetitive elements in the absence of MBD4 in vivo. Methylation mark loss is accompanied by a broad transcriptional derepression phenotype affecting promoters and retroelements with low methylated CpG density. MBD4 in vivo forms a complex with the mismatch repair proteins (MMR), which exhibits high bi-functional glycosylase/AP-lyase endonuclease specific activity towards methylated DNA substrates containing a G/T mismatch. Experiments using recombinant proteins reveal that the association of MBD4 with the MMR protein MLH1 is required for this activity. The described data identify MBD4 as an enzyme specifically designed to repair deaminated 5-methylcytosines and illustrates how MBD4 functions in normal and pathological conditions.

ORGANISM(S): Mus musculus

PROVIDER: GSE84497 | GEO | 2022/01/10

REPOSITORIES: GEO

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MBD4 loss results in global reactivation of promoters and retroelements with low methylated CpG density.

Project description:Inherited defects in the base-excision repair gene MBD4 predispose individuals to adenomatous polyposis and colorectal cancer, which is characterized by an accumulation of C>T transitions resulting from spontaneous deamination of 5’-methylcytosine. Despite its significance, this DNA repair pathway is still poorly understood. Here we show that the protein MBD4 is required for DNA methylation maintenance and G/T mismatch repair. Transcriptome and methylome analyses reveal a genome-wide hypomethylation of promoters, gene bodies and repetitive elements in the absence of MBD4 in vivo. Methylation mark loss is accompanied by a broad transcriptional derepression phenotype affecting promoters and retroelements with low methylated CpG density. MBD4 in vivo forms a complex with the mismatch repair proteins (MMR), which exhibits high bi-functional glycosylase/AP-lyase endonuclease specific activity towards methylated DNA substrates containing a G/T mismatch. Experiments using recombinant proteins reveal that the association of MBD4 with the MMR protein MLH1 is required for this activity. The described data identify MBD4 as an enzyme specifically designed to repair deaminated 5-methylcytosines and illustrates how MBD4 functions in normal and pathological conditions.

2022-01-10 | GSE84319 | GEO

MBD4 loss results in global reactivation of promoters and retroelements with low methylated CpG density.

2022-01-10 | GSE84318 | GEO

Expression data from control and Mbd4 KO CH12 cells that were activated with CIT for 24 hours.

Project description:AID-dependent U/G mismatches in S DNA are converted by BER and MMR DNA pathways into double-stranded breaks that are required for optimal CSR in activated B cells. Deficits in MMR proteins, MSH2, MLH1, and PMS2 result in lower CSR frequencies that are coupled with impaired DSB formation. MBD4 interacts with MLH1 and has been postulated to coordinate mismatch repair of U/G. Deletions of Mbd4 targeting the 5' end of the gene in mice do not affect CSR . However, Mbd4 transcription is complex, with the propensity to create alternative transcripts, including residual transcription leading to to truncated protein expression that complicates ananlysis in these mice. We describe a novel function of MBD4 housed in the C-terminus that is critical for DSB formation, which shares several characteristics with MMR . We conclude that the 3' end of the Mbd4 gene positively contributes to CSR and likely intersects the MMR pathway. 2 independent samples for each control and Mbd4 KO group

2013-12-19 | E-GEOD-51559 | biostudies-arrayexpress

Expression data from control and Mbd4 KO CH12 cells that were activated with CIT for 24 hours.

2013-12-19 | GSE51559 | GEO

DNA mismatch repair activity of MutLalpha is regulated by CK2-dependent phosphorylation of MLH1

Project description:Mass spectrometry based PTM phosphorylation analysis to study regulation mechanism of MUTL alpha, a heterodimer consisting of MLH1 and PMS2 and a key player in DNA mismatch repair (MMR). It could be demonstrated that phosphorylation of MLH1 by Casein Kinase II (CK2) at amino acid position 477 can switch off MMR activity in vitro.

2018-08-29 | PXD009026 | Pride

High-resolution mapping of heteroduplex DNA formed in UV-induced and spontaneous mitotic recombination events in yeast

Project description:In yeast, DNA breaks are usually repaired by homologous recombination (HR). An early step for HR pathways is formation of a heteroduplex, in which a single-strand from the broken DNA molecule pairs with a strand derived from an intact DNA molecule. If the two strands of DNA are not identical, there will be mismatches within the heteroduplex DNA (hetDNA). In wild-type strains, these mismatches are repaired by the mismatch repair (MMR) system, producing a gene conversion event. In strains lacking MMR, the mismatches persist. Most previous studies involving hetDNA formed during mitotic recombination were restricted to one locus. Below, we present a global mapping of hetDNA formed in the MMR-defective mlh1 strain. We find that many recombination events are associated with repair of double-stranded DNA gaps and/or involve Mlh1-independent mismatch repair. Many of our events are not explicable by the simplest form of the double-strand break repair model of recombination.

2017-06-27 | GSE100497 | GEO

DNA mismatch repair activity of MutLα is regulated by CK2-dependent phosphorylation of MLH1 (S477)

Project description:MutLα, a heterodimer consisting of MLH1 and PMS2, is a key player of DNA mismatch repair (MMR), yet little is known about its regulation. In this study, we used mass spectrometry to identify phosphorylated residues within MLH1 and PMS2. The most frequently detected phosphorylated amino acid was serine 477 of MLH1. Isolation of nuclear and cytoplasmic fractions showed that p-MLH1S477 remains predominantly in the cytoplasm. Pharmacological treatment indicates that Casein Kinase II (CK2) could be responsible for the phosphorylation of MLH1 at serine 477 in vivo. In vitro kinase assay verified MLH1 as a substrate of CK2. Most importantly, using in vitro MMR assay we could demonstrate that p-MLH1S477 lost MMR activity while the activity of MLH1S477A, which could not be phosphorylated at position S477, was not modified. In summary, we identified that post-translational phosphorylation of MLH1 by CK2 at amino acid position 477 can switch off MMR activity in vitro. Since CK2 is overexpressed in many tumors and is able to inactivate MMR by phosphorylation of MLH1, the new mechanism here described could have an important impact on tumors overactive in CK2.

2018-08-28 | PXD009524 | Pride

Mismatch-repair signature mutations activate gene enhancers across human colorectal cancer epigenomes

Project description:We show that mismatch-repair (MMR) signature mutations can activate colorectal cancer (CRC)-specific enhancers, through analysis of enhancer DNA associated with the active enhancer histone mark H3K27ac. We demonstrate that MMR mutations activate enhancers using a xenograft metastasis model, where mutations are induced naturally via CRISPR/Cas9 inactivation of MLH1 prior to tumor cell injection.

2019-02-07 | GSE126188 | GEO

Expression data from primary gastric tumors (MSI and MSS) and adjacent normal samples

Project description:Gastric cancers with mismatch repair (MMR) inactivation are characterised by microsatellite instability (MSI). In this study, the transcriptional profile of 38 gastric cancers with and without MSI was analysed. Unsupervised analysis showed that the immune and apoptotic gene networks efficiently discriminated these two cancer types. Hierarchical clustering analysis revealed numerous gene expression changes associated with the MSI phenotype. Amongst these, the p53-responsive genes maspin and 14-3-3 sigma were significantly more expressed in tumours with than without MSI. A tight immunosurveillance coupled with a functional p53 gene response is consistent with the better prognosis of MSI cancers. Frequent silencing of MLH1 and downregulation of MMR target genes, such as MRE11 and MBD4, characterised MSI tumours. The downregulation of SMUG1 was also a typical feature of these tumours. The DNA repair gene expression profile of gastric cancer with MSI is of relevance for therapy response.

2008-12-18 | GSE13911 | GEO

Dual FAN1 activities stabilize the HTT CAG repeat

Project description:Recent data strongly suggest HTT CAG repeat expansion drives Huntington’s disease (HD) pathogenesis and that disease development is modulated by components of the DNA damage response (DDR) pathway. FAN1 has been identified as a major HD modifier which slows expansion of the HTT CAG repeat in several cell and animal HD models. Here we show dual FAN1 activities act to inhibit repeat expansion. A highly conserved SPYF motif in the FAN1 N-terminus is required for an MLH1 interaction, which slows expansion, with FAN1 nuclease activity also contributing towards repeat stabilisation. Our data supports a model where FAN1 binds MLH1, restricting its recruitment by MSH3 and the formation of the functional DNA mismatch repair (MMR) complex believed to promote CAG repeat expansion. FAN1 nuclease activity functions either concurrently or following MMR activity to maintain repeat stability. These data highlight a potential avenue for HD therapeutics in attenuating somatic expansion.

2022-02-16 | PXD023221 | Pride

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