近期,国际著名学术期刊PNAS(《美国科学院院报》)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。该成果表明乙酰化酶PCAF对微管正端示踪蛋白EB1的修饰可以精细调控细胞有丝分裂过程中染色体着丝粒(动点)与微管的连接,该调控分子机制的阐明为癌症的治疗提供了一条新的线索。
细胞精确的自我复制是其生活史的重要组成部分,复制的高保真性在生物及物种的繁衍生息过程中举足轻重。有丝分裂过程中染色体精确均等地分配到两个子细胞中对于生命的延续与健康至关重要,若染色体的分配发生错误,则会导致非整倍体和染色体不稳定性的发生并且增加罹患癌症的风险。有丝分裂的顺利完成依赖于双极纺锤体的形成、染色体沿纺锤体微管轨道精确移动、染色体通过着丝粒寻找并捕获纺锤体微管正末端,在这个连续的过程中,微管正端示踪蛋白具有至关重要的作用。微管末端结合蛋白1(End-binding protein 1, EB1)作为微管正端示踪蛋白机器的核心分子,定位于动点与微管连接处,可以招募和调控其它微管正端示踪蛋白在动点-微管连接处行使功能。
研究组综合利用生物光子学、细胞生物学和结构生物学技术手段,揭示了着丝粒相关的乙酰化酶PCAF可以特异性地对EB1蛋白的220位赖氨酸进行乙酰化修饰,这个修饰影响了EB1蛋白中一个疏水窝状结构的稳定性,而这个疏水窝正是介导微管示踪蛋白与EB1蛋白结合的关键部分,因此该乙酰化修饰会影响整个微管示踪蛋白机器的组装。实验结果还发现EB1蛋白该位点的乙酰化修饰水平在有丝分裂期增高,另外表达模拟乙酰化的EB1蛋白的细胞中,染色体排列在赤道板时会出现延迟,并持续激活有丝分裂中期检验点。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机制及其在染色体稳定性维系中的功能。该调控机制的阐明对于进一步理解有丝分裂的精密调控具有重要意义。(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.
Xia P, Wang Z, Liu X, Wu B, Wang J, Ward T, Zhang L, Ding X, Gibbons G, Shi Y, Yao X.
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.