文章基本信息

标题：Methylated DNA-binding domain 1 and methylpurine–DNA glycosylase link transcriptional repression and DNA repair in chromatin
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作者：Sugiko Watanabe ; Takaya Ichimura ; Naoyuki Fujita 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：22
页码：12859-12864
DOI：10.1073/pnas.2131819100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The methyl-CpG dinucleotide containing a symmetrical 5-methylcytosine (mC) is involved in gene regulation and genome stability. We report here that methylation-mediated transcriptional repressor methylated DNA-binding domain 1 (MBD1) interacts with methylpurine-DNA glycosylase (MPG), which excises damaged bases from substrate DNA. MPG itself actively represses transcription and has a synergistic effect on gene silencing together with MBD1. Chromatin immunoprecipitation analysis reveals the molecular movement of MBD1 and MPG in vivo: (i) The MBD1-MPG complex normally exists on the methylated gene promoter; (ii) treatment of cells with alkylating agent methylmethanesulfonate (MMS) induces the dissociation of MBD1 from the methylated promoter, and MPG is located on both methylated and unmethylated promoters; and (iii) after completion of the repair, the MBD1-MPG complex is restored on the methylated promoter. Mobility-shift and structural analyses show that the MBD of MBD1 binds a methyl-CpG pair (mCpG x mCpG) but not the methyl-CpG pair containing a single 7-methylguanine (N) (mCpG x mCpN) that is known as one of the major lesions caused by MMS. We further demonstrate that knockdown of MBD1 by specific small interfering RNAs significantly increases cell sensitivity to MMS. These data suggest that MBD1 cooperates with MPG for transcriptional repression and DNA repair. We hypothesize that MBD1 functions as a reservoir for MPG and senses the base damage in chromatin.