Institute of Life Sciences, Bhubaneswar, Odisha 751023, India.
Regional Centre for Biotechnology, Faridabad 121001, Haryana, India.
Plant Cell. 2022 Nov 29;34(12):4760-4777. doi: 10.1093/plcell/koac275.
Histone acetyltransferase (HAT)- and histone deacetylase (HDAC)-mediated histone acetylation and deacetylation regulate nucleosome dynamics and gene expression. HDACs are classified into different families, with HD-tuins or HDTs being specific to plants. HDTs show some sequence similarity to nucleoplasmins, the histone chaperones that aid in binding, storing, and loading H2A/H2B dimers to assemble nucleosomes. Here, we solved the crystal structure of the N-terminal domain (NTD) of all four HDTs (HDT1, HDT2, HDT3, and HDT4) from Arabidopsis (Arabidopsis thaliana). The NTDs form a nucleoplasmin fold, exist as pentamers in solution, and are resistant to protease treatment, high temperature, salt, and urea conditions. Structurally, HDTs do not form a decamer, unlike certain classical nucleoplasmins. The HDT-NTD requires an additional A2 acidic tract C-terminal to the nucleoplasmin domain for interaction with histone H3/H4 and H2A/H2B oligomers. We also report the in-solution structures of HDT2 pentamers in complex with histone oligomers. Our study provides a detailed structural and in vitro functional characterization of HDTs, revealing them to be nucleoplasmin family histone chaperones. The experimental confirmation that HDTs are nucleoplasmins may spark new interest in this enigmatic family of proteins.
组蛋白乙酰转移酶 (HAT) 和组蛋白去乙酰化酶 (HDAC) 介导的组蛋白乙酰化和去乙酰化调节核小体动力学和基因表达。HDAC 分为不同的家族，HD-tuins 或 HDTs 是植物特有的。HDTs 与核质蛋白（histone chaperones）具有一定的序列相似性，核质蛋白有助于结合、储存和加载 H2A/H2B 二聚体以组装核小体。在这里，我们解析了拟南芥（Arabidopsis thaliana）中所有四种 HDTs（HDT1、HDT2、HDT3 和 HDT4）的 N 端结构域（NTD）的晶体结构。NTDs 形成核质蛋白折叠，以五聚体形式存在于溶液中，并能抵抗蛋白酶处理、高温、盐和尿素条件。结构上，HDTs 不像某些经典核质蛋白那样形成十聚体。HDT-NTD 需要核质蛋白结构域 C 末端额外的 A2 酸性片段与组蛋白 H3/H4 和 H2A/H2B 寡聚物相互作用。我们还报告了 HDT2 五聚体与组蛋白寡聚物复合物在溶液中的结构。我们的研究提供了 HDTs 的详细结构和体外功能特征，揭示了它们是核质蛋白家族的组蛋白伴侣。实验证实 HDTs 是核质蛋白，可能会激发人们对这个神秘的蛋白质家族的新兴趣。
