Ekblad Caroline M S, Chavali Gayatri B, Basu Balaka P, Freund Stefan M V, Veprintsev Dmitry, Hughes-Davies Luke, Kouzarides Tony, Doherty Aidan J, Itzhaki Laura S
MRC Cancer Cell Unit, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 2XZ, UK.
EMBO Rep. 2005 Jul;6(7):675-80. doi: 10.1038/sj.embor.7400415.
EMSY is a large nuclear protein that binds to the transactivation domain of BRCA2. EMSY contains an approximately 100-residue segment at the amino terminus called the ENT (EMSY N-terminal) domain. Plant proteins containing ENT domains also contain members of the royal family of chromatin-remodelling domains. It has been proposed that EMSY may have a role in chromatin-related processes. This is supported by the observation that a number of chromatin-regulator proteins, including HP1beta and BS69, bind directly to EMSY by means of a conserved motif adjacent to the ENT domain. Here, we report the crystal structure of residues 1-108 of EMSY at 2.0 A resolution. The structure contains both the ENT domain and the HP1beta/BS69-binding motif. This binding motif forms an extended peptide-like conformation that adopts distinct orientations in each subunit of the dimer. Biophysical and nuclear magnetic resonance analyses show that the main complex formed by EMSY and the chromoshadow domain of HP1 (HP1-CSD) consists of one EMSY dimer sandwiched between two HP1-CSD dimers. The HP1beta-binding motif is necessary and sufficient for EMSY to bind to the chromoshadow domain of HP1beta.
EMSY是一种大型核蛋白，可与BRCA2的反式激活结构域结合。EMSY在氨基末端含有一个约100个残基的片段，称为ENT（EMSY N末端）结构域。含有ENT结构域的植物蛋白也包含染色质重塑结构域王室成员。有人提出EMSY可能在染色质相关过程中发挥作用。这一观点得到了如下观察结果的支持：包括HP1β和BS69在内的许多染色质调节蛋白通过与ENT结构域相邻的保守基序直接与EMSY结合。在此，我们报告了EMSY 1-108位残基的晶体结构，分辨率为2.0埃。该结构包含ENT结构域和HP1β/BS69结合基序。这种结合基序形成一种延伸的肽样构象，在二聚体的每个亚基中采取不同的取向。生物物理和核磁共振分析表明，EMSY与HP1的染色体阴影结构域（HP1-CSD）形成的主要复合物由夹在两个HP1-CSD二聚体之间的一个EMSY二聚体组成。HP1β结合基序对于EMSY与HP1β的染色体阴影结构域结合是必要且充分的。
