Klose Robert J, Sarraf Shireen A, Schmiedeberg Lars, McDermott Suzanne M, Stancheva Irina, Bird Adrian P
Wellcome Trust Centre for Cell Biology, Michael Swann Building, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom.
Mol Cell. 2005 Sep 2;19(5):667-78. doi: 10.1016/j.molcel.2005.07.021.
DNA methylation is interpreted by a family of methyl-CpG binding domain (MBD) proteins that repress transcription through recruitment of corepressors that modify chromatin. To compare in vivo binding of MeCP2 and MBD2, we analyzed immunoprecipitated chromatin from primary human cells. Genomic sites occupied by the two MBD proteins were mutually exclusive. As MeCP2 was unable to colonize sites vacated by depletion of MBD2, we tested the hypothesis that methyl-CpG alone is insufficient to direct MeCP2 binding. In vitro selection for MeCP2 bound DNA-enriched fragments containing A/T bases ([A/T] > or = 4) adjacent to methyl-CpG. [A/T] > or = 4 was found to be essential for high-affinity binding at selected sites and at known MeCP2 target regions in the Bdnf and Dlx6 genes. MBD2 binding, however, did not require an A/T run. The unexpected restriction of MeCP2 to a defined subset of methyl-CpG sites will facilitate identification of genomic targets that are relevant to Rett Syndrome.
DNA甲基化由一类甲基化CpG结合结构域（MBD）蛋白进行解读，这些蛋白通过招募修饰染色质的共抑制因子来抑制转录。为了比较MeCP2和MBD2在体内的结合情况，我们分析了来自原代人类细胞的免疫沉淀染色质。这两种MBD蛋白占据的基因组位点是相互排斥的。由于MeCP2无法定位于因MBD2缺失而空出的位点，我们测试了甲基化CpG单独不足以指导MeCP2结合的假说。体外筛选与甲基化CpG相邻含有A/T碱基（[A/T]≥4）的MeCP2结合的富含DNA片段。发现[A/T]≥4对于在选定位点以及Bdnf和Dlx6基因中已知的MeCP2靶区域进行高亲和力结合至关重要。然而，MBD2的结合并不需要A/T序列。MeCP2对甲基化CpG位点特定子集的意外限制将有助于鉴定与雷特综合征相关的基因组靶点。
