Wordeman Linda, Wagenbach Michael, von Dassow George
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA.
J Cell Biol. 2007 Dec 3;179(5):869-79. doi: 10.1083/jcb.200707120. Epub 2007 Nov 26.
Mitotic centromere-associated kinesin (MCAK)/Kif2C is the most potent microtubule (MT)-destabilizing enzyme identified thus far. However, MCAK's function at the centromere has remained mechanistically elusive because of interference from cytoplasmic MCAK's global regulation of MT dynamics. In this study, we present MCAK chimeras and mutants designed to target centromere-associated MCAK for mechanistic analysis. Live imaging reveals that depletion of centromere-associated MCAK considerably decreases the directional coordination between sister kinetochores. Sister centromere directional antagonism results in decreased movement speed and increased tension. Sister centromeres appear unable to detach from kinetochore MTs efficiently in response to directional switching cues during oscillatory movement. These effects are reversed by anchoring ectopic MCAK to the centromere. We propose that MCAK increases the turnover of kinetochore MTs at all centromeres to coordinate directional switching between sister centromeres and facilitate smooth translocation. This may contribute to error correction during chromosome segregation either directly via slow MT turnover or indirectly by mechanical release of MTs during facilitated movement.
有丝分裂着丝粒相关驱动蛋白（MCAK）/Kif2C是迄今为止所鉴定出的最有效的微管（MT）去稳定化酶。然而，由于细胞质MCAK对MT动力学的全局调控产生干扰，MCAK在着丝粒处的功能在机制上仍不明确。在本研究中，我们展示了为靶向着丝粒相关MCAK进行机制分析而设计的MCAK嵌合体和突变体。实时成像显示，着丝粒相关MCAK的缺失显著降低了姐妹动粒之间的方向协调性。姐妹着丝粒方向拮抗导致移动速度降低和张力增加。在振荡运动期间，姐妹着丝粒似乎无法有效地响应方向转换信号而从动粒微管上脱离。通过将异位MCAK锚定到着丝粒上，这些效应得以逆转。我们提出，MCAK增加了所有着丝粒处动粒微管的周转，以协调姐妹着丝粒之间的方向转换，并促进平滑易位。这可能直接通过缓慢的微管周转或通过在易化运动期间微管的机械释放间接有助于染色体分离过程中的错误校正。
