Periodic DNA methylation in maize nucleosomes and demethylation by environmental stress
Periodic DNA methylation in maize nucleosomes and demethylation by environmental stress
复制标题
DOI：
10.1074/jbc.m204050200
复制
发表时间：
2002-10-04
影响因子：
4.8
通讯作者：
Sano, H
中科院分区：
文献类型：
--
作者：
Steward, N;Ito, M;Sano, H
低温胁迫下，玉米根组织发生了全基因组范围的去甲基化。基因组DNA的筛选确定了一个特定的片段，是在低温脱甲基化。这个1.8 kb的片段，命名为ZmMI 1，含有一个推定的蛋白质的编码区的一部分和一个逆转录转座子样序列的一部分。ZmMI 1仅在低温胁迫下转录。直接甲基化图谱显示，跨越150个碱基的低甲基化区域与跨越50个碱基的高甲基化区域交替。用微球菌核酸酶消化的核DNA的分析表明，这些区域分别对应于核小体核心和接头。冷应激诱导严重的核心区域去甲基化，但左连接区相对完整。因此，甲基化和去甲基化在核小体中是周期性的。以下生物学意义是可以想象的。首先，由于核小体中的DNA甲基化通过改变染色质结构来诱导基因表达的改变，因此大量的去甲基化可能是许多基因的共同开关，这些基因同时受到环境线索的控制。第二，因为人工去甲基化诱导植物表型的可遗传变化（佐野，H.，卡马达岛Youssefian，S.，Katsumi，M.，和Wabilko，H.（1990）Mol. Genet将军220，441-447），改变的DNA甲基化可能导致表观遗传，其中基因表达被修饰而不改变核苷酸序列。
When maize seedlings were exposed to cold stress, a genome-wide demethylation occurred in root tissues. Screening of genomic DNA identified one particular fragment that was demethylated during chilling. This 1.8-kb fragment, designated ZmMI1, contained part of the coding region of a putative protein and part of a retrotransposon-like sequence. ZmMI1 was transcribed only under cold stress. Direct methylation mapping revealed that hypomethylated regions spanning 150 bases alternated with hypermethylated regions spanning 50 bases. Analysis of nuclear DNA digested with micrococcal nuclease indicated that these regions corresponded to nucleosome cores and linkers, respectively. Cold stress induced severe demethylation in core regions but left linker regions relatively intact. Thus, methylation and demethylation were periodic in nucleosomes. The following biological significance is conceivable. First, because DNA methylation in nucleosomes induces alteration of gene expression by changing chromatin structures, vast demethylation may serve as a common switch for many genes that are simultaneously controlled upon environmental cues. Second, because artificial demethylation induces heritable changes in plant phenotype (Sano, H., Kamada, I., Youssefian, S., Katsumi, M., and Wabilko, H. (1990) Mol. Gen. Genet. 220, 441-447), altered DNA methylation may result in epigenetic inheritance, in which gene expression is modified without changing the nucleotide sequence.