Ohi Ryoma, Coughlin Margaret L, Lane William S, Mitchison Timothy J
Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
Dev Cell. 2003 Aug;5(2):309-21. doi: 10.1016/s1534-5807(03)00229-6.
Mitosis requires precise control of microtubule dynamics. The KinI kinesin MCAK, a microtubule depolymerase, is critical for this regulation. In a screen to discover previously uncharacterized microtubule-associated proteins, we identified ICIS, a protein that stimulates MCAK activity in vitro. Consistent with this biochemical property, blocking ICIS function in Xenopus extracts with antibodies caused excessive microtubule growth and inhibited spindle formation. Prior to anaphase, ICIS localized in an MCAK-dependent manner to inner centromeres, the chromosomal region located in between sister kinetochores. From Xenopus extracts, ICIS coimmunoprecipitated MCAK and the inner centromere proteins INCENP and Aurora B, which are thought to promote chromosome biorientation. By immunoelectron microscopy, we found that ICIS is present on the surface of inner centromeres, placing it in an ideal location to depolymerize microtubules associated laterally with inner centromeres. At inner centromeres, MCAK-ICIS may destabilize these microtubules and provide a mechanism that prevents kinetochore-microtubule attachment errors.
有丝分裂需要对微管动力学进行精确控制。Kini驱动蛋白MCAK是一种微管解聚酶，对这种调节至关重要。在一项旨在发现此前未被鉴定的微管相关蛋白的筛选中，我们鉴定出了ICIS，一种在体外刺激MCAK活性的蛋白。与这种生化特性一致，用抗体阻断非洲爪蟾提取物中的ICIS功能会导致微管过度生长并抑制纺锤体形成。在后期之前，ICIS以MCAK依赖的方式定位于内着丝粒，即位于姐妹动粒之间的染色体区域。在非洲爪蟾提取物中，ICIS与MCAK以及内着丝粒蛋白INCENP和Aurora B共同免疫沉淀，这些蛋白被认为可促进染色体双定向。通过免疫电子显微镜，我们发现ICIS存在于内着丝粒表面，使其处于一个理想的位置来解聚与内着丝粒横向相关的微管。在内着丝粒处，MCAK-ICIS可能会使这些微管不稳定，并提供一种防止动粒-微管附着错误的机制。
