title: Epigenomic stress response. Knockdown of DNA methyltransferase 1 triggers an intra-S-phase arrest of DNA replication and induction of stress response genes.
abstract: The DNA methylation pattern is an important component of the epigenome that regulates and maintains gene expression programs. In this paper, we test the hypothesis that vertebrate cells possess mechanisms protecting them from epigenomic stress similar to DNA damage checkpoints. We show that knockdown of DNMT1 (DNA methyltransferase 1) by an antisense oligonucleotide triggers an intra-S-phase arrest of DNA replication that is not observed with control oligonucleotide. The cells are arrested at different positions throughout the S-phase of the cell cycle, suggesting that this response is not specific to distinct classes of origins of replication. The intra-S-phase arrest of DNA replication is proposed to protect the genome from extensive DNA demethylation that could come about by replication in the absence of DNMT1. This protective mechanism is not induced by 5-aza-2'-deoxycytidine, a nucleoside analog that inhibits DNA methylation by trapping DNMT1 in the progressing replication fork, but does not reduce de novo synthesis of DNMT1. Our data therefore suggest that the intra-S-phase arrest is triggered by a reduction in DNMT1 and not by demethylation of DNA. DNMT1 knockdown also leads to an induction of a set of genes that are implicated in genotoxic stress response such as NF-kappaB, JunB, ATF-3, and GADD45beta (growth arrest DNA damage 45beta gene). Based on these data, we suggest that this stress response mechanism evolved to guard against buildup of DNA methylation errors and to coordinate inheritance of genomic and epigenomic information.
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 1Y6, Canada.
authors.forename: Snezana
authors.initials: S
authors.lastname: Milutinovic
authors.forename: Qianli
authors.initials: Q
authors.lastname: Zhuang
authors.forename: Alain
authors.initials: A
authors.lastname: Niveleau
authors.forename: Moshe
authors.initials: M
authors.lastname: Szyf
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors / Q000502:physiology*; D019175:DNA Methylation; D004260:DNA Repair / Q000235:genetics; D004261:DNA Replication / Q000187:drug effects / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D009687:Nuclear Proteins / Q000096:biosynthesis; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D016196:S Phase / Q000187:drug effects
chemical_list: D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D004248:DNA (Cytosine-5-)-Methyltransferases