Oxidative Damage Targets Complexes Containing DNA Methyltransferases, SIRT1, and Polycomb Members to Promoter CpG Islands

SummaryCancer cells simultaneously harbor global losses and gains in DNA methylation. We demonstrate that inducing cellular oxidative stress by hydrogen peroxide treatment recruits DNA methyltransferase 1 (DNMT1) to damaged chromatin. DNMT1 becomes part of a complex(es) containing DNMT3B and members of the polycomb repressive complex 4. Hydrogen peroxide treatment causes relocalization of these proteins from non-GC-rich to GC-rich areas. Key components are similarly enriched at gene promoters in an in vivo colitis model. Although high-expression genes enriched for members of the complex have histone mark and nascent transcription changes, CpG island-containing low-expression genes gain promoter DNA methylation. Thus, oxidative damage induces formation and relocalization of a silencing complex that may explain cancer-specific aberrant DNA methylation and transcriptional silencing.

► DNMT1 becomes more tightly bound to chromatin after oxidative damage
► Oxidative damage induces formation of a complex containing DNMT1, DNMT3B and PRC4
► DNMT-PRC4 enrichment at CpG islands may explain aberrant gene silencing in cancer
► Promoters enriched for these proteins have histone mark and DNA methylation changes