Functional coordination of BET family proteins

Bromodomain and extraterminal proteins (BET) are epigenetic adaptors that play critical roles in gene regulation. This protein family contains two conserved bromodomains which can mediate the interaction with acetylated histone lysine residues and/or other acetylated proteins, and one extraterminal (ET) domain. BET protein inhibition has been recognized as a promising therapeutic strategy for several diseases, including acute myeloid leukaemia, castration resistant prostate cancer, and triple negative breast cancer. BET inhibition by a specific inhibitor JQ1 caused an impairment in various brain functions but the underlying molecular mechanisms are not well understood. Among BET family members, BRD4 has been recognized for its prominent role in epigenetic regulation of gene expression. However, we have found an extensive functional redundancy and coordination among all three major BET family members (BRD2/3/4) during the activity-dependent gene induction in neurons, which is also reflected in learning and memory behavior. Our study further revealed the molecular hierarchy in the coordination of BET family proteins dissecting their distinctive functions during gene induction required for proper brain function and plasticity. Understanding the functional coordination of BET family proteins at the molecular level would be beneficial to the development of more selective interventions for various diseases that are caused by dysregulated epigenetic pathways. Overall design: mRNA-, nascent RNA-, or ChIP-seq profiles were generated from primary mouse cortical neurons at DIV7, comparing untreated neurons to neurons treated with different stimuli for different length of time or from Fmr1 KO with littermate control in duplicate

溴结构域与额外末端结构域蛋白（Bromodomain and extraterminal proteins, BET）是一类在基因调控中发挥关键作用的表观遗传适配蛋白。该蛋白家族包含两个保守的溴结构域，可介导与乙酰化组蛋白赖氨酸残基或其他乙酰化蛋白的相互作用，以及一个额外末端（ET）结构域。BET蛋白抑制已被认定为多种疾病的潜在治疗策略，涵盖急性髓系白血病、去势抵抗性前列腺癌与三阴性乳腺癌。采用特异性抑制剂JQ1抑制BET可导致多种脑功能受损，但其背后的分子机制尚未得到充分阐释。在BET家族成员中，BRD4因在基因表达的表观遗传调控中发挥核心作用而备受关注。然而，我们的研究发现，在神经元的活性依赖型基因诱导过程中，BET家族三大核心成员（BRD2/3/4）之间存在广泛的功能冗余与协同调控，这一特征在学习记忆行为中亦有所体现。本研究进一步揭示了BET家族蛋白协同作用的分子层级关系，解析了它们在维持正常脑功能与脑可塑性所需的基因诱导过程中各自的独特功能。从分子层面解析BET家族蛋白的功能协同机制，将有助于开发针对表观遗传通路失调所致多种疾病的更具选择性的干预手段。实验设计：从体外培养第7天（days in vitro 7, DIV）的原代小鼠皮层神经元中制备样本，生成信使RNA（mRNA）测序、新生RNA（nascent RNA）测序及染色质免疫共沉淀测序（ChIP-seq）的谱图数据，设置两类比较实验组：其一为未处理神经元与经不同刺激物处理不同时长的神经元；其二为Fmr1敲除（Fmr1 knockout, Fmr1 KO）小鼠神经元与其同窝对照小鼠神经元，所有样本均设置双份生物学重复。