Delaney Kamila, Almouzni Geneviève
Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics Unit, Equipe Labellisée Ligue contre le Cancer, 26 rue d'Ulm, 75005 Paris, France.
Semin Cell Dev Biol. 2023 Feb 15;135:13-23. doi: 10.1016/j.semcdb.2022.05.003. Epub 2022 May 18.
Histone variant H3.3 is incorporated into chromatin throughout the cell cycle and even in non-cycling cells. This histone variant marks actively transcribed chromatin regions with high nucleosome turnover, as well as silent pericentric and telomeric repetitive regions. In the past few years, significant progress has been made in our understanding of mechanisms involved in the transcription-coupled deposition of H3.3. Here we review how, during transcription, new H3.3 deposition intermingles with the fate of the old H3.3 variant and its recycling. First, we describe pathways enabling the incorporation of newly synthesized vs old H3.3 histones in the context of transcription. We then review the current knowledge concerning differences between these two H3.3 populations, focusing on their PTMs composition. Finally, we discuss the implications of H3.3 recycling for the maintenance of the transcriptional state and underline the emerging importance of H3.3 as a potent epigenetic regulator for both maintaining and switching a transcriptional state.
组蛋白变体H3.3在整个细胞周期甚至非循环细胞中都能整合到染色质中。这种组蛋白变体标记了具有高核小体周转率的活跃转录染色质区域，以及沉默的着丝粒和端粒重复区域。在过去几年中，我们对参与H3.3转录偶联沉积机制的理解取得了重大进展。在这里，我们回顾了在转录过程中，新的H3.3沉积如何与旧的H3.3变体的命运及其循环利用相互交织。首先，我们描述了在转录背景下使新合成的与旧的H3.3组蛋白得以整合的途径。然后，我们回顾了关于这两种H3.3群体之间差异的现有知识，重点关注它们的翻译后修饰（PTM）组成。最后，我们讨论了H3.3循环利用对维持转录状态的影响，并强调了H3.3作为维持和切换转录状态的有效表观遗传调节因子的重要性日益凸显。
