Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
J Biol Chem. 2023 Aug;299(8):104996. doi: 10.1016/j.jbc.2023.104996. Epub 2023 Jun 30.
A critical component of gene regulation is recognition of histones and their post-translational modifications by transcription-associated proteins or complexes. Although many histone-binding reader modules have been characterized, the bromo-adjacent homology (BAH) domain family of readers is still poorly characterized. A pre-eminent member of this family is PBRM1 (BAF180), a component of the PBAF chromatin-remodeling complex. PBRM1 contains two adjacent BAH domains of unknown histone-binding potential. We evaluated the tandem BAH domains for their capacity to associate with histones and to contribute to PBAF-mediated gene regulation. The BAH1 and BAH2 domains of human PBRM1 broadly interacted with histone tails, but they showed a preference for unmodified N-termini of histones H3 and H4. Molecular modeling and comparison of the BAH1 and BAH2 domains with other BAH readers pointed to a conserved binding mode via an extended open pocket and, in general, an aromatic cage for histone lysine binding. Point mutants that were predicted to disrupt the interaction between the BAH domains and histones reduced histone binding in vitro and resulted in dysregulation of genes targeted by PBAF in cellulo. Although the BAH domains in PBRM1 were important for PBAF-mediated gene regulation, we found that overall chromatin targeting of PBRM1 was not dependent on BAH-histone interaction. Our findings identify a function of the PBRM1 BAH domains in PBAF activity that is likely mediated by histone tail interaction.
基因调控的一个关键组成部分是转录相关蛋白或复合物识别组蛋白及其翻译后修饰。虽然已经鉴定出许多组蛋白结合阅读器模块，但溴邻结构域（BAH）家族的阅读器仍然知之甚少。该家族的杰出成员是 PBRM1（BAF180），它是 PBAF 染色质重塑复合物的一个组成部分。PBRM1 包含两个相邻的、具有未知组蛋白结合潜力的 BAH 结构域。我们评估了串联 BAH 结构域与组蛋白结合的能力及其对 PBAF 介导的基因调控的贡献。人 PBRM1 的 BAH1 和 BAH2 结构域与组蛋白尾部广泛相互作用，但它们对组蛋白 H3 和 H4 的未修饰 N 端具有偏好性。分子建模和 BAH1 和 BAH2 结构域与其他 BAH 阅读器的比较表明，通过扩展的开放口袋和一般的芳香笼，存在保守的结合模式，用于组蛋白赖氨酸结合。预测会破坏 BAH 结构域与组蛋白之间相互作用的点突变降低了体外的组蛋白结合，并导致 PBAF 在细胞内靶向的基因失调。虽然 PBRM1 中的 BAH 结构域对于 PBAF 介导的基因调控很重要，但我们发现 PBRM1 的总体染色质靶向并不依赖于 BAH-组蛋白相互作用。我们的研究结果确定了 PBRM1 BAH 结构域在 PBAF 活性中的一个功能，该功能可能是通过组蛋白尾部相互作用介导的。
