Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.
These authors contributed equally to this work.
Mol Cells. 2021 Feb 28;44(2):79-87. doi: 10.14348/molcells.2021.2242.
Chromatin dynamics is essential for maintaining genomic integrity and regulating gene expression. Conserved bromodomain-containing AAA+ ATPases play important roles in nucleosome organization as histone chaperones. Recently, the high-resolution cryo-electron microscopy structures of Abo1 revealed that it forms a hexameric ring and undergoes a conformational change upon ATP hydrolysis. In addition, single-molecule imaging demonstrated that Abo1 loads H3-H4 histones onto DNA in an ATP hydrolysis-dependent manner. However, the molecular mechanism by which Abo1 loads histones remains unknown. Here, we investigated the details concerning Abo1-mediated histone loading onto DNA and the Abo1- DNA interaction using single-molecule imaging techniques and biochemical assays. We show that Abo1 does not load H2A-H2B histones. Interestingly, Abo1 deposits multiple copies of H3-H4 histones as the DNA length increases and requires at least 80 bp DNA. Unexpectedly, Abo1 weakly binds DNA regardless of ATP, and neither histone nor DNA stimulates the ATP hydrolysis activity of Abo1. Based on our results, we propose an allosteric communication model in which the ATP hydrolysis of Abo1 changes the configuration of histones to facilitate their deposition onto DNA.
染色质动力学对于维持基因组完整性和调节基因表达至关重要。保守的含溴结构域的 AAA+ATP 酶作为组蛋白伴侣，在核小体组织中发挥重要作用。最近，Abo1 的高分辨率冷冻电镜结构揭示了它形成六聚体环，并在 ATP 水解时发生构象变化。此外，单分子成像表明 Abo1 以 ATP 水解依赖性方式将 H3-H4 组蛋白加载到 DNA 上。然而，Abo1 加载组蛋白的分子机制尚不清楚。在这里，我们使用单分子成像技术和生化测定研究了 Abo1 介导的组蛋白加载到 DNA 上的详细情况以及 Abo1-DNA 相互作用。我们表明 Abo1 不会加载 H2A-H2B 组蛋白。有趣的是，Abo1 随着 DNA 长度的增加而沉积多个 H3-H4 组蛋白拷贝，并且至少需要 80bp 的 DNA。出乎意料的是，Abo1 无论有无 ATP 都能弱结合 DNA，并且组蛋白和 DNA 都不会刺激 Abo1 的 ATP 水解活性。根据我们的结果，我们提出了一个变构通讯模型，其中 Abo1 的 ATP 水解改变组蛋白的构象，以促进其沉积到 DNA 上。
