Yang Xiao, Wu Xuelei, Zhang Jiahai, Zhang Xuecheng, Xu Chao, Liao Shanhui, Tu Xiaoming
School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
School of Life Sciences, Anhui University, Hefei, Anhui, China.
Biochem J. 2017 Nov 9;474(22):3817-3830. doi: 10.1042/BCJ20170619.
Histone modification plays an important role in various biological processes, including gene expression regulation. Bromodomain, as one of histone readers, recognizes specifically the ε--lysine acetylation (KAc) of histone. Although the bromodomains and histone acetylation sites of (), a lethal parasite responsible for sleeping sickness in human and nagana in cattle, have been identified, how acetylated histones are recognized by bromodomains is still unknown. Here, the bromodomain factor 2 (TbBDF2) from was identified to be located in the nucleolus and bind to the hyperacetylated N-terminus of H2AZ which dimerizes with H2BV. The bromodomain of TbBDF2 (TbBDF2-BD) displays a conserved fold that comprises a left-handed bundle of four α-helices (αZ, αA, αB, αC), linked by loop regions of variable length (ZA and BC loops), which form the KAc-binding pocket. NMR chemical shift perturbation further revealed that TbBDF2-BD binds to the hyperacetylated N-terminus of H2AZ through its KAc-binding pocket. By structure-based virtual screening combining with the ITC experiment, a small molecule compound, GSK2801, was shown to have high affinity to TbBDF2-BD. GSK2801 and the hyperacetylated N-terminus of H2AZ have similar binding sites on TbBDF2-BD. In addition, GSK2801 competitively inhibits the hyperacetylated N-terminus of H2AZ binding to TbBDF2-BD. After treatment of GSK2801, cell growth was inhibited and localization of TbBDF2 was disrupted. Our results report a novel bromodomain-histone recognition by TbBDF2-BD and imply that TbBDF2 may serve as a potential chemotherapeutic target for the treatment of trypanosomiasis.
组蛋白修饰在包括基因表达调控在内的各种生物学过程中发挥着重要作用。作为组蛋白阅读器之一的溴结构域，能特异性识别组蛋白的ε-赖氨酸乙酰化（KAc）。尽管已鉴定出导致人类昏睡病和牛锥虫病的致命寄生虫（）的溴结构域和组蛋白乙酰化位点，但溴结构域如何识别乙酰化组蛋白仍不清楚。在这里，来自的溴结构域因子2（TbBDF2）被鉴定位于核仁，并与与H2BV二聚化的H2AZ的高乙酰化N端结合。TbBDF2的溴结构域（TbBDF2-BD）呈现出保守的折叠结构，由四个左手螺旋（αZ、αA、αB、αC）组成，通过可变长度的环区域（ZA和BC环）连接，这些环区域形成了KAc结合口袋。核磁共振化学位移扰动进一步表明，TbBDF2-BD通过其KAc结合口袋与H2AZ的高乙酰化N端结合。通过基于结构的虚拟筛选结合ITC实验，一种小分子化合物GSK2801被证明对TbBDF2-BD具有高亲和力。GSK2801和H2AZ的高乙酰化N端在TbBDF2-BD上具有相似的结合位点。此外，GSK2801竞争性抑制H2AZ的高乙酰化N端与TbBDF2-BD的结合。用GSK2801处理后，细胞生长受到抑制，TbBDF2的定位被破坏。我们的结果报道了TbBDF2-BD对溴结构域-组蛋白的一种新识别方式，并暗示TbBDF2可能作为治疗锥虫病的潜在化疗靶点。
