title: MBD4 and MLH1 are required for apoptotic induction in xDNMT1-depleted embryos.
abstract: Loss of the of the maintenance methyltransferase xDNMT1 during Xenopus development results in premature transcription and activation of a p53-dependent apoptotic program that accounts for embryo lethality. Here, we show that activation of the apoptotic response is signalled through the methyl-CpG binding protein xMBD4 and the mismatch repair pathway protein xMLH1. Depletion of xMBD4 or xMLH1 increases the survival rate of xDNMT1-depleted embryos, whereas overexpression of these proteins in embryos induces programmed cell death at the onset of gastrulation. MBD4 interacts directly with both DNMT1 and MLH1, leading to recruitment of the latter to heterochromatic sites that are coincident with DNMT1 localisation. Time-lapse microscopy of micro-irradiated mammalian cells shows that MLH1/MBD4 (like DNMT1) can accumulate at DNA damage sites. We propose that xMBD4/xMLH1 participates in a novel G2 checkpoint that is responsive to xDNMT1p levels in developing embryos and cells.
authors.affiliation: Human Genetics Unit, MRC, IGMM, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
authors.forename: Alexey
authors.initials: A
authors.lastname: Ruzov
authors.forename: Boris
authors.initials: B
authors.lastname: Shorning
authors.forename: Oliver
authors.initials: O
authors.lastname: Mortusewicz
authors.forename: Donncha S
authors.initials: DS
authors.lastname: Dunican
authors.forename: Heinrich
authors.initials: H
authors.lastname: Leonhardt
authors.forename: Richard R
authors.initials: RR
authors.lastname: Meehan
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D006570:Heterochromatin / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays; D014981:Xenopus; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D006570:Heterochromatin; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D029867:Xenopus Proteins; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; C000619382:Dnmt1 protein, rat; D004706:Endodeoxyribonucleases; D045643:DNA Repair Enzymes