SET7/9-MCAK相互作用调控有丝分裂染色体运动的功能解析

Chromosome segregation in mitosis is orchestrated by the dynamic interactions between the kinetochore and spindle microtubules. The microtubule depolymerase mitotic centromere-associated kinesin (MCAK) is a key regulator of mitotic spindle plasticity. However, the regulatory mechanism underlying precise MCAK depolymerase activity control during mitosis remains elusive. Our previous study identify a novel MCAK interacting protein SET7/9, which is a histone lysine methyltransferase, it can also methylate a series of non-histone proteins. Depletion of SET7/9 by RNA interference causes a prolonged delay in achieving metaphase alignment and aberrant anaphase with chromosome mis-segregation. Further research also found that SET7/9 may engage in the regulation of mitosis by methylation of MCAK. Based on these findings, our study aims to identify MCAK as a new mitotic substrate of SET7/9 methyltransferase, to evaluate dynamic regulation process of MCAK depolymerase activity by methylation and to illustrate the functional mechanisms of MCAK methylation in the regulation of mitotic spindle plasticity, thereby affecting the kinetochore-microtubule interaction and faithful chromosome segregation. Taken together, our project will reveal a new regulation mechanism of mitotic spindle plasticity, illustrate a new significance of non-histone protein methylation and to lay the foundation for comprehensive understanding the mitotic regulation mechanism of methylation.

有丝分裂染色体的精确分离依赖于动点和纺锤体微管的动态衔接。微管解聚酶MCAK是有丝分裂纺锤体可塑性的主要调节者之一，但其在有丝分裂中的解聚酶活性调节机制还不是很清楚。我们的前期工作发现了一个新的MCAK结合蛋白SET7/9，后者是已知的组蛋白甲基转移酶，同时也被报道可以甲基化一系列非组蛋白。当用RNA干扰技术敲低细胞内SET7/9蛋白水平，中期染色体队列延迟，并导致后期染色体错误分离。进一步的研究还发现SET7/9可能通过甲基化MCAK参与有丝分裂。为此，我们拟通过本项目鉴定甲基转移酶SET7/9对有丝分裂关键性蛋白MCAK的甲基化修饰，评估甲基化对MCAK微管解聚酶活性的动态调节，阐明甲基化MCAK调控纺锤体可塑性，进而影响动点-微管连接和染色体分离的功能机制。总体上，我们力争揭示有丝分裂纺锤体动力学调控的新机制，阐明非组蛋白甲基化修饰的新意义，为全面了解甲基化调控有丝分裂奠定工作基础。

有丝分裂染色体的精确分离依赖于动点和纺锤体微管的动态衔接，这涉及到一系列微管结合蛋白和动点激酶的调控。我们的研究发现SET7/9甲基转移酶可以甲基化MCAK和Plk1，分别通过SET7/9-MCAK-AuroraB和SET7/9-Plk1-BubR1两个信号轴调节MCAK微管解聚酶活性和Plk1激酶活性，进而影响动点-微管连接。当甲基化被抑制，中期染色体队列延迟，并导致后期染色体错误分离。通过该项目的执行，我们解析了有丝分裂相关非组蛋白甲基化修饰的新分子机制，为阐明甲基化对细胞周期的调节奠定了工作基础。

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