近期，国际著名学术期刊PNAS在线发表了中国科学技术大学生命科学学院施蕴渝教授与姚雪彪教授研究组的合作成果。文章标题为EB1 acetylation by P300/CBP-associated factor (PCAF) ensures accurate kinetochore-microtubule interactions in mitosis。该成果揭示了微管正端示踪蛋白EB1被乙酰化酶PCAF修饰并精细调控细胞有丝分裂染色体着丝粒（动点）与微管连接的分子机制。文章第一作者为中国科学技术大学生命科学院博士生夏鹏和王志凯。
有丝分裂顺利完成依赖于双极纺锤体的形成以及染色体沿纺锤体微管轨道的精确移动。染色体通过着丝粒寻找以及捕获纺锤体微管正末端，在这一过程中，微管正端示踪蛋白超家族具有至关重要的作用。在有丝分裂过程中，微管末端结合蛋白1（End-binding protein 1, EB1)作为微管正端示踪蛋白超家族的核心分子，定位于动点与微管连接处，并招募和调控微管正端示踪蛋白超家族在动点-微管连接中行使功能。利用结构生物学引导的功能分析法，本项研究成果证明着丝粒相关的乙酰化酶PCAF特异性地对EB1的220位赖氨酸进行乙酰化修饰，进而影响到EB1分子中一个疏水窝状结构的稳定性，而这个疏水窝正是介导其他微管示踪蛋白结合EB1分子的关键部分。进而该乙酰化修饰会影响整个微管示踪蛋白超复合物的组装。同时，EB1的220位赖氨酸乙酰化特异性识别抗体揭示该乙酰化修饰水平在细胞进入有丝分裂期时有增高趋势。表达模拟乙酰化突变体EB1的细胞在有丝分裂中期染色体排列在赤道板时出现延迟，并使得有丝分裂中期检验点持续激活。该项研究首次发现翻译后修饰对于微管正端示踪蛋白超复合物组装的时空动力学调控，并通过这种调控影响和控制染色体着丝粒与微管之间的连接。该调控机制的阐明对于理解有丝分裂精密调控具有重大意义，并为阻断癌症细胞增殖提供了新的靶点。（生物谷Bioon.com）
doi: 10.1073/pnas.1202639109
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EB1 acetylation by P300/CBP-associated factor (PCAF) ensures accurate kinetochore–microtubule interactions in mitosis
Peng Xia, Zhikai Wang, Xing Liu, Bing Wu, Juncheng Wang, Tarsha Ward, Liangyu Zhang, Xia Ding, Gary Gibbons, Yunyu Shi, and Xuebiao Yao
In eukaryotes, microtubules are essential for cellular plasticity and dynamics. Here we show that P300/CBP-associated factor (PCAF), a kinetochore-associated acetyltransferase, acts as a negative modulator of microtubule stability through acetylation of EB1, a protein that controls the plus ends of microtubules. PCAF acetylates EB1 on K220 and disrupts the stability of a hydrophobic cavity on the dimerized EB1 C terminus, which was previously reported to interact with plus-end tracking proteins (TIPs) containing the SxIP motif. As determined with an EB1 acetyl-K220–specific antibody, K220 acetylation is dramatically increased in mitosis and localized to the spindle microtubule plus ends. Surprisingly, persistent acetylation of EB1 delays metaphase alignment, resulting in impaired checkpoint silencing. Consequently, suppression of Mad2 overrides mitotic arrest induced by persistent EB1 acetylation. Thus, our findings identify dynamic acetylation of EB1 as a molecular mechanism to orchestrate accurate kinetochore–microtubule interactions in mitosis. These results establish a previously uncharacterized regulatory mechanism governing localization of microtubule plus-end tracking proteins and thereby the plasticity and dynamics of cells.
