Cross-talk between MECP2 post-translational modifications and MECP2 function upon glucocorticoid stress hormone stimulation

MeCP2(甲基CpG结合蛋白2)是一种中枢性表观遗传调节因子，它通过与甲基化的DNA结合并募集组蛋白修饰酶，在全基因组水平上控制染色质结构和转录状态。MeCP2对中枢神经系统的正常运作起着至关重要的作用，MECP2基因的突变与人类严重的神经系统疾病(如雷特综合征，女性第二常见的人类精神发育迟滞疾病)有关。重要的是，MECP2翻译后修饰已被确定为该蛋白的关键调控水平。值得注意的是，MECP2的磷酸化与神经元的活动和应激有关。在MECP2相互作用蛋白的蛋白质组筛选中，我们发现MECP2与PARP-1相互作用并被PARP-1聚合(ADP-核糖)。我们发现这种修饰调节了MECP2与染色质结合和缩合的能力。在对MECP2修饰的单独筛查中，我们发现，除了其他修饰外，MECP2在脑组织中是精氨酸甲基化的。非常有可能的是，翻译后修饰的类型和不同修饰的MECP2蛋白的基因组定位是微调和多样化整个基因组中神经细胞MECP2功能的方法。然而，人们对特定的MECP2修饰的影响知之甚少。在这个项目中，我们将系统地研究MECP2在糖皮质激素刺激下发生的翻译后修饰，并研究它们在调节海马细胞染色质结构和基因活性中的作用。在我们初步结果的基础上，我们将重点研究聚(ADP-核糖基)和精氨酸甲基化，并将它们与磷酸化联系起来。我们的具体目标是：i)表征MECP2翻译后修饰(PTM)及其在应激激素处理后的变化；ii)分析PTM是否以及如何影响MECP2蛋白质的相互作用；iii)测试这些修饰与MECP2染色质结合、染色质结构和转录调控的功能相关性；iv)分析PTM如何受疾病突变的MECP2基因产生的MECP2蛋白的影响或影响其功能。这项工作将有助于阐明MECP2在生理和病理生理条件下的作用，并为MECP2相关神经疾病的病因学提供重要线索。由于翻译后修饰非常适合于药物抑制，它还应该概述新的治疗方法。

MECP2 (methyl CpG binding protein 2) is a central epigenetic regulator, it controls chromatin structure and transcriptional state at a genome-wide level by binding to methylated DNA and recruiting histone modifying enzymes. MECP2 plays an essential role for the proper functioning of the central nervous system and mutations in the MECP2 gene are linked to severe neurological disorders in humans (such as Rett syndrome, the second most common human mental retardation disorder in females). Importantly, post-translational MECP2 modifications have been identified as a critical level of regulation of this protein. Notably, MECP2 phosphorylation has been linked to neuronal activity and stress. In a proteomic screen for MECP2 interacting proteins we have found that MECP2 interacts with and is poly(ADP-ribosyl)ated by PARP-1. We showed that this modification modulates MECP2 ability to bind to and condense chromatin. In a separate screen for MECP2 modifications we found, amongst other modifications, that MECP2 is arginine methylated in brain tissue. It is highly conceivable that the type of posttranslational modification and the genomic localization of differently modified MECP2 proteins are ways to fine tune and diversify MECP2 function in neuronal cells across the genome. However, very little is known about the effects of specific MECP2 modifications. In this project, we will investigate, in a systematic way, MECP2 post-translational modifications that occur upon stimulation with glucocorticoid stress hormones and study their role in regulating chromatin structure and gene activity in hippocampal cells. Building upon our preliminary results, we will focus on poly(ADP-ribosyl)ation and arginine methylation and relate these with phosphorylation. Our specific aims are to: i) characterize MECP2 post-translational modifications (PTMs) and their change upon stress hormone treatment; ii) analyze whether and how PTMs affect MECP2 protein interactions; iii) test the functional relevance of these modifications for MECP2 chromatin binding, chromatin structure and transcriptional regulation; iv) analyze how PTMs are affected by or affect the function of MECP2 proteins produced by disease mutant MECP2 genes. This work should significantly contribute to the elucidation of the role of MECP2 under physiological and pathophysiological conditions and provide important clues as to the etiology of MECP2-related neurological disorders. As post-translational modifications are very suited to pharmacological inhibition, it should also outline new therapeutic approaches.