Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada V8W 3P6.
Nucleic Acids Res. 2012 Apr;40(7):2884-97. doi: 10.1093/nar/gkr1066. Epub 2011 Dec 5.
Methyl-CpG-binding protein 2 (MeCP2) is a chromatin-binding protein that mediates transcriptional regulation, and is highly abundant in brain. The nature of its binding to reconstituted templates has been well characterized in vitro. However, its interactions with native chromatin are less understood. Here we show that MeCP2 displays a distinct distribution within fractionated chromatin from various tissues and cell types. Artificially induced global changes in DNA methylation by 3-aminobenzamide or 5-aza-2'-deoxycytidine, do not significantly affect the distribution or amount of MeCP2 in HeLa S3 or 3T3 cells. Most MeCP2 in brain is chromatin-bound and localized within highly nuclease-accessible regions. We also show that, while in most tissues and cell lines, MeCP2 forms stable complexes with nucleosome, in brain, a fraction of it is loosely bound to chromatin, likely to nucleosome-depleted regions. Finally, we provide evidence for novel associations of MeCP2 with mononucleosomes containing histone H2A.X, H3K9me(2) and H3K27me(3) in different chromatin fractions from brain cortex and in vitro. We postulate that the functional compartmentalization and tissue-specific distribution of MeCP2 within different chromatin types may be directed by its association with nucleosomes containing specific histone variants, and post-translational modifications.
甲基化 CpG 结合蛋白 2（MeCP2）是一种染色质结合蛋白，介导转录调控，在大脑中含量丰富。其在体外重组模板上的结合性质已得到很好的描述。然而，其与天然染色质的相互作用还不太清楚。在这里，我们展示了 MeCP2 在来自不同组织和细胞类型的分级染色质中表现出明显的分布。通过 3-氨基苯甲酰胺或 5-氮杂-2'-脱氧胞苷人工诱导的 DNA 甲基化的全局变化，不会显著影响 HeLa S3 或 3T3 细胞中 MeCP2 的分布或数量。大脑中的大多数 MeCP2 与染色质结合，并定位于高度核酸酶可及的区域。我们还表明，虽然在大多数组织和细胞系中，MeCP2 与核小体形成稳定的复合物，但在大脑中，一部分 MeCP2 与染色质松散结合，可能与核小体缺失区域结合。最后，我们提供了证据表明，MeCP2 与来自大脑皮层不同染色质部分和体外的含有组蛋白 H2A.X、H3K9me(2) 和 H3K27me(3) 的单核小体存在新的关联。我们推测，MeCP2 在不同染色质类型中的功能区室化和组织特异性分布可能是由其与含有特定组蛋白变体和翻译后修饰的核小体的关联所指导的。
