School of Life Sciences, Jilin University, 2699 Qianjin Street, Changchun 130012, China.
National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Nucleic Acids Res. 2022 Jan 11;50(1):191-206. doi: 10.1093/nar/gkab1221.
Histone variants have been implicated in regulating chromatin dynamics and genome functions. Previously, we have shown that histone variant H3.3 actively marks enhancers and cooperates with H2A.Z at promoters to prime the genes into a poised state in mouse embryonic stem cells (mESCs). However, how these two important histone variants collaboratively function in this process still remains elusive. In this study, we found that depletion of different components of HIRA complex, a specific chaperone of H3.3, results in significant decreases of H2A.Z enrichment at genome scale. In addition, CUT&Tag data revealed a genomic colocalization between HIRA complex and SRCAP complex. In vivo and in vitro biochemical assays verified that HIRA complex could interact with SRCAP complex through the Hira subunit. Furthermore, our chromatin accessibility and transcription analyses demonstrated that HIRA complex contributed to preset a defined chromatin feature around TSS region for poising gene transcription. In summary, our results unveiled that while regulating the H3.3 incorporation in the regulatory regions, HIRA complex also collaborates with SRCAP to deposit H2A.Z onto the promoters, which cooperatively determines the transcriptional potential of the poised genes in mESCs.
组蛋白变体被认为在调节染色质动力学和基因组功能方面发挥作用。先前，我们已经表明，组蛋白变体 H3.3 可以积极标记增强子，并与启动子处的 H2A.Z 合作，使基因在小鼠胚胎干细胞 (mESC) 中处于预先激活状态。然而，这两种重要的组蛋白变体如何在这个过程中协同发挥作用仍然难以捉摸。在这项研究中，我们发现 HIRA 复合物的不同成分（H3.3 的特定伴侣蛋白）耗竭后，基因组范围内 H2A.Z 的富集显著减少。此外，CUT&Tag 数据显示 HIRA 复合物和 SRCAP 复合物在基因组上存在共定位。体内和体外生化测定验证了 HIRA 复合物可以通过 Hira 亚基与 SRCAP 复合物相互作用。此外，我们的染色质可及性和转录分析表明，HIRA 复合物有助于在 TSS 区域周围预先设定特定的染色质特征，以激活基因转录。总之，我们的结果揭示了 HIRA 复合物在调节调控区域的 H3.3 掺入的同时，还与 SRCAP 合作将 H2A.Z 沉积到启动子上，这共同决定了 mESC 中预先激活基因的转录潜力。
