Huang Tzu-Lun, Wang Hsiu-Jung, Chang Ya-Chieh, Wang Shao-Win, Hsia Kuo-Chiang
Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and National Defense Medical Center, Taipei 11490, Taiwan; Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan.
Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan.
Cell Rep. 2020 Jun 30;31(13):107836. doi: 10.1016/j.celrep.2020.107836.
How γ-tubulin ring complex (γ-TuRC), a master template for microtubule nucleation, is spatially and temporally regulated for the assembly of new microtubule arrays remains unclear. Here, we report that an evolutionarily conserved microprotein, Mozart1 (Mzt1), regulates subcellular targeting and microtubule formation activity of γ-TuRC at different cell cycle stages. Crystal structures of protein complexes demonstrate that Mzt1 promiscuously interacts with the N-terminal domains of multiple γ-tubulin complex protein subunits in γ-TuRC via an intercalative binding mode. Genetic- and microscopy-based analyses show that promiscuous binding of Mzt1 in γ-TuRC controls specific subcellular localization of γ-TuRC to modulate microtubule nucleation and stabilization in fission yeast. Moreover, we find Mzt1-independent targeting of γ-TuRC to be crucial for mitotic spindle assembly, demonstrating the cell-cycle-dependent regulation and function of γ-TuRC. Our findings reveal a microprotein-mediated regulatory mechanism underlying microtubule cytoskeleton formation, whereby Mzt1 binding promiscuity confers localization specificity on the multi-protein complex γ-TuRC.
作为微管成核的主要模板，γ-微管蛋白环复合物（γ-TuRC）如何在空间和时间上受到调控以组装新的微管阵列仍不清楚。在此，我们报告一种进化上保守的微蛋白，莫扎特1（Mzt1），在不同细胞周期阶段调节γ-TuRC的亚细胞定位和微管形成活性。蛋白质复合物的晶体结构表明，Mzt1通过插入结合模式与γ-TuRC中多个γ-微管蛋白复合蛋白亚基的N端结构域杂乱地相互作用。基于遗传学和显微镜的分析表明，Mzt1在γ-TuRC中的杂乱结合控制γ-TuRC的特定亚细胞定位，以调节裂殖酵母中的微管成核和稳定性。此外，我们发现γ-TuRC的Mzt1非依赖性靶向对于有丝分裂纺锤体组装至关重要，这证明了γ-TuRC的细胞周期依赖性调控和功能。我们的研究结果揭示了微管细胞骨架形成背后的一种微蛋白介导的调控机制，其中Mzt1结合的杂乱性赋予多蛋白复合物γ-TuRC定位特异性。
