AUTS2 confers transcriptional activation to PRC1 in the CNS (ChIP-Seq)

Naturally occurring variations of Polycomb Repressive Complex 1 (PRC1) comprise a core assembly of Polycomb group proteins and additional factors that include, surprisingly, Autism Susceptibility Candidate 2 (AUTS2). While AUTS2 is often disrupted in patients with neuronal disorders, the underlying mechanism is unclear. We investigated the role of AUTS2 as part of a previously identified PRC1 complex (PRC1-AUTS2), and in the context of neurodevelopment. In contrast to the canonical role of PRC1 in gene repression, PRC1-AUTS2 activates transcription. Biochemical studies demonstrate that the CK2 component of PRC1-AUTS2 thwarts PRC1 repressive activity and AUTS2-mediated recruitment of P300 leads to gene activation. ChIP-seq of AUTS2 shows that it regulates neuronal gene expression through promoter association. Conditional CNS targeting of Auts2 in a mouse model leads to various developmental defects. These findings reveal a natural means of subverting PRC1 activity, linking key epigenetic modulators with neuronal functions and diseases. ChIP-seq experiments of PRC1 components, PolII as well as histone modifications were performed either in mouse whole brain or in human 293T-REx lines expressing FLAG/HA-tagged subunits. RNA-seq was performed to analyze the expression profile of mouse whole brain.

天然存在的多梳抑制复合体1（Polycomb Repressive Complex 1, PRC1）变体由多梳家族蛋白核心组装体与附加调控因子组成，其中意外包含自闭症易感候选因子2（Autism Susceptibility Candidate 2, AUTS2）。尽管AUTS2在神经系统疾病患者中常发生功能紊乱，但其背后的分子机制仍不明晰。本研究针对此前已鉴定的PRC1复合体（PRC1-AUTS2）中的AUTS2功能，及其在神经发育进程中的作用开展了系统探究。与PRC1经典的基因转录抑制功能相悖，PRC1-AUTS2复合体可激活基因转录。生化实验证实，PRC1-AUTS2中的CK2组分可拮抗PRC1的转录抑制活性，而AUTS2介导的P300招募则可介导基因激活。针对AUTS2的染色质免疫共沉淀测序（Chromatin Immunoprecipitation sequencing, ChIP-seq）结果表明，其通过结合基因启动子调控神经元基因的表达水平。在小鼠模型中对Auts2进行中枢神经系统条件性靶向操作，可诱发多种发育异常表型。本研究揭示了一种天然的PRC1活性拮抗机制，将关键表观遗传调控因子与神经元生理功能及疾病发生直接关联。本研究分别在小鼠全脑组织，或表达FLAG/HA标签融合亚基的人源293T-REx细胞系中，完成了PRC1组分、RNA聚合酶II（RNA Polymerase II, PolII）以及组蛋白修饰的ChIP-seq实验；同时通过RNA测序（RNA sequencing, RNA-seq）分析小鼠全脑的基因表达谱。