Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, WI, 53706, USA.
Wisconsin Institute for Discovery, University of Wisconsin, Madison, WI, 53715, USA.
Nat Commun. 2017 Oct 30;8(1):1193. doi: 10.1038/s41467-017-01206-y.
The ATRX-DAXX histone chaperone complex incorporates the histone variant H3.3 at heterochromatic regions in a replication-independent manner. Here, we present a high-resolution x-ray crystal structure of an interaction surface between ATRX and DAXX. We use single amino acid substitutions in DAXX that abrogate formation of the complex to explore ATRX-dependent and ATRX-independent functions of DAXX. We find that the repression of specific murine endogenous retroviruses is dependent on DAXX, but not on ATRX. In support, we reveal the existence of two biochemically distinct DAXX-containing complexes: the ATRX-DAXX complex involved in gene repression and telomere chromatin structure, and a DAXX-SETDB1-KAP1-HDAC1 complex that represses endogenous retroviruses independently of ATRX and H3.3 incorporation into chromatin. We find that histone H3.3 stabilizes DAXX protein levels and can affect DAXX-regulated gene expression without incorporation into nucleosomes. Our study demonstrates a nucleosome-independent function for the H3.3 histone variant.
ATRX-DAXX 组蛋白伴侣复合物以复制独立的方式将组蛋白变体 H3.3 纳入异染色质区域。在这里，我们呈现了 ATRX 和 DAXX 之间相互作用表面的高分辨率 X 射线晶体结构。我们使用在 DAXX 中导致复合物形成缺失的单点氨基酸取代来探索 DAXX 的 ATRX 依赖性和 ATRX 非依赖性功能。我们发现，特定的鼠内源性逆转录病毒的抑制依赖于 DAXX，但不依赖于 ATRX。支持这一发现，我们揭示了两种具有不同生化特性的 DAXX 包含复合物的存在：ATRX-DAXX 复合物参与基因抑制和端粒染色质结构，以及 DAXX-SETDB1-KAP1-HDAC1 复合物，它独立于 ATRX 和 H3.3 掺入染色质来抑制内源性逆转录病毒。我们发现组蛋白 H3.3 稳定了 DAXX 蛋白水平，并可以影响 DAXX 调节的基因表达，而无需掺入核小体。我们的研究证明了 H3.3 组蛋白变体的核小体非依赖性功能。
