Nan X, Meehan R R, Bird A
Institute of Cell and Molecular Biology, University of Edinburgh, UK.
Nucleic Acids Res. 1993 Oct 25;21(21):4886-92. doi: 10.1093/nar/21.21.4886.
MeCP2 is a chromosomal protein which binds to DNA that is methylated at CpG. In situ immunofluorescence in mouse cells has shown that the protein is most concentrated in pericentromeric heterochromatin, suggesting that MeCP2 may play a role in the formation of inert chromatin. Here we have isolated a minimal methyl-CpG binding domain (MBD) from MeCP2. MBD is 85 amino acids in length, and binds exclusively to DNA that contains one or more symmetrically methylated CpGs. MBD has negligable non-specific affinity for DNA, confirming that non-specific and methyl-CpG specific binding domains of MeCP2 are distinct. In vitro footprinting indicates that MBD binding can protect a 12 nucleotide region surrounding a methyl-CpG pair, with an approximate dissociation constant of 10(-9) M.
MeCP2是一种与在CpG处甲基化的DNA结合的染色体蛋白。小鼠细胞中的原位免疫荧光显示，该蛋白最集中在着丝粒周围的异染色质中，这表明MeCP2可能在惰性染色质的形成中起作用。在此，我们从MeCP2中分离出一个最小的甲基化CpG结合结构域（MBD）。MBD长度为85个氨基酸，并且仅与含有一个或多个对称甲基化CpG的DNA结合。MBD对DNA的非特异性亲和力可忽略不计，这证实了MeCP2的非特异性和甲基化CpG特异性结合结构域是不同的。体外足迹分析表明，MBD结合可以保护甲基化CpG对周围的12个核苷酸区域，其解离常数约为10^(-9) M。
