Department of Biological Science and Technology, Faculty of Advanced Engineering, Tokyo University of Science (TUS), 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan.
Acta Crystallogr F Struct Biol Commun. 2022 May 1;78(Pt 5):193-199. doi: 10.1107/S2053230X22003843. Epub 2022 Apr 22.
The CENP-SX (MHF) complex is a conserved histone-fold protein complex that is involved in chromosome segregation and DNA repair. It can bind to DNA on its own as well as in complex with other proteins such as CENP-TW and FANCM to recognize specific substrates. CENP-SX binds nonspecifically to dsDNA, similar to other histone-fold proteins. Several low-resolution structures of CENP-SX in complex with DNA are known, but a high-resolution structure is still lacking. The DNA-binding properties of CENP-SX and FANCM-CENP-SX complexes with various lengths of dsDNA were compared and the band-shift patterns and migration positions were found to differ. To confirm the DNA-binding properties in detail, CENP-SX-DNA and FANCM-CENP-SX-DNA complexes were crystallized. Analysis of the crystals revealed that they all contained the CENP-SX-DNA complex, irrespective of the complex that was used in crystallization. Detailed diffraction data analyses revealed that there were two types of crystal with different space groups, P2 and C2, where the volume of the P2 asymmetric unit is twice as large as that of the C2 asymmetric unit. Analysis of the self-rotation function revealed the presence of twofold and fourfold symmetry in both crystals. This suggests that there may be multiple molecules of CENP-SX and DNA within the asymmetric unit with respective symmetry. Structure determination of the present crystals should reveal details of the DNA-binding properties of CENP-SX.
CENP-SX（MHF）复合物是一种保守的组蛋白折叠蛋白复合物，参与染色体分离和 DNA 修复。它可以单独结合 DNA，也可以与其他蛋白质（如 CENP-TW 和 FANCM）结合，以识别特定的底物。CENP-SX 与 dsDNA 非特异性结合，类似于其他组蛋白折叠蛋白。已知 CENP-SX 与 DNA 复合物的几个低分辨率结构，但仍缺乏高分辨率结构。比较了 CENP-SX 和 FANCM-CENP-SX 与不同长度 dsDNA 的复合物的 DNA 结合特性，发现带迁移模式和迁移位置不同。为了详细确认 DNA 结合特性，对 CENP-SX-DNA 和 FANCM-CENP-SX-DNA 复合物进行了结晶。晶体分析表明，无论用于结晶的复合物如何，它们都包含 CENP-SX-DNA 复合物。详细的衍射数据分析表明，存在两种具有不同空间群的晶体，P2 和 C2，其中 P2 不对称单元的体积是 C2 不对称单元的两倍。自旋转函数分析表明，两种晶体都存在二倍和四倍对称。这表明在不对称单元中可能存在多个 CENP-SX 和 DNA 分子，具有各自的对称性。目前晶体的结构测定应揭示 CENP-SX 的 DNA 结合特性的细节。
