Liu Zhonghua, Li Fudong, Zhang Beibei, Li Sai, Wu Jihui, Shi Yunyu
From the Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, China.
From the Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, China
J Biol Chem. 2015 Mar 6;290(10):6630-8. doi: 10.1074/jbc.M114.610196. Epub 2015 Jan 19.
The NuRD complex is a conserved transcriptional coregulator that contains both chromatin-remodeling and histone deacetylase activities. Mutations of PHF6 are found in patients with Börjeson-Forssman-Lehmann syndrome, T-cell acute lymphoblastic leukemia, or acute myeloid leukemia. Recently, PHF6 was identified to interact with the NuRD complex, and this interaction is mediated by the RBBP4 component. However, little is known about the molecular basis for the interaction. Here, we present the crystal structure of the complex of the NuRD subunit RBBP4 bound to the PHF6 peptide (residues 162-170). The PHF6 peptide binds to the top surface of the RBBP4 β-propeller. A pair of positively charged residues of the PHF6 peptide insert into the negatively charged pocket of RBBP4, which is critical for the interaction between PHF6 and RBBP4. Corresponding PHF6 mutants impair this interaction in vitro and in vivo. Structural comparison shows that the PHF6-binding pocket overlaps with FOG1 and histone H3 on RBBP4/Nurf55, but it is distinct from the pocket recognizing histone H4, Su(z)12, and MTA1. We further show that the middle disordered region (residues 145-207, containing the RBBP4-binding motif) is sufficient for the transcriptional repression mediated by PHF6 on the GAL4 reporter, and knockdown of RBBP4 diminished the PHF6-mediated repression. Our RBBP4-PHF6 complex structure provides insights into the molecular basis of PHF6-NuRD complex interaction and implicates a role for PHF6 in chromatin structure modulation and gene regulation.
核小体重塑去乙酰化酶复合物（NuRD复合物）是一种保守的转录共调节因子，兼具染色质重塑和组蛋白去乙酰化活性。在博耶森 - 福斯曼 - 莱曼综合征、T细胞急性淋巴细胞白血病或急性髓系白血病患者中发现了PHF6的突变。最近，发现PHF6与NuRD复合物相互作用，且这种相互作用由RBBP4组分介导。然而，关于这种相互作用的分子基础知之甚少。在此，我们展示了与PHF6肽（第162 - 170位残基）结合的NuRD亚基RBBP4复合物的晶体结构。PHF6肽结合在RBBP4β - 螺旋桨的顶面。PHF6肽的一对带正电荷的残基插入到RBBP4带负电荷的口袋中，这对PHF6与RBBP4之间的相互作用至关重要。相应的PHF6突变体在体外和体内均损害这种相互作用。结构比较表明，PHF6结合口袋与RBBP4 / Nurf55上的FOG1和组蛋白H3重叠，但与识别组蛋白H4、Su(z)12和MTA1的口袋不同。我们进一步表明，中间无序区域（第145 - 207位残基，包含RBBP4结合基序）足以介导PHF6对GAL4报告基因的转录抑制，敲低RBBP4会减弱PHF6介导的抑制作用。我们的RBBP4 - PHF6复合物结构为PHF6 - NuRD复合物相互作用的分子基础提供了见解，并暗示了PHF6在染色质结构调节和基因调控中的作用。
