MeCP2, a transcriptional repressor, is post-translationally regulated by protein arginine methylation
Rett syndrome, associated with a variety of mutations in the MECP2 gene in ∼80% of the cases examined, is poorly understood. Although the protein product of MeCP2 is a DNA-binding protein, the cellular regulation of the protein function has yet to be elucidated fully. Based on the presence of three GRG consensus sites for arginine methylation within MeCP2, experiments were designed to determine whether post-translational methylation occurs in intact cells in a manner that may be regulated during neuronal development. Disruption of any one of the three GRG sites in recombinant MeCP2 eliminates or markedly reduces in vitro methylation. Methylation of recombinant MeCP2 increases binding to methyl-CpG DNA measured by mobility shift and southwestern assays. Methylated MeCP2 also exhibits greater association with co-repressor Sin3A than non-methylated MeCP2. A methylarginine-specific antiserum, anti-mRG, detects methylated MeCP2 in intact rat PC12 and hippocampal cells. NGF and BDNF treatment of PC12 and hippocampal cells, respectively, leads to increased anti-mRG reactivity toward MeCP2. In addition, we also employed ChIP and RT-PCR assays to demonstrate that the repression of BDNF gene expression by extracellular BDNF occurs via increasing MeCP2 methylation. These studies provide the first demonstration of MeCP2 methylation in a neurotrophin-dependent manner and the regulation of BDNF gene by MeCP2 methylation.