Koffa Maria D, Casanova Claudia M, Santarella Rachel, Köcher Thomas, Wilm Matthias, Mattaj Iain W
EMBL, Heidelberg, Germany.
Curr Biol. 2006 Apr 18;16(8):743-54. doi: 10.1016/j.cub.2006.03.056.
GTP-loaded Ran induces the assembly of microtubules into aster-like and spindle-like structures in Xenopus egg extract. The microtubule-associated protein (MAP), TPX2, can mediate Ran's role in aster formation, but factors responsible for the transition from aster-like to spindle-like structures have not been described.
Here we identify a complex that is required for the conversion of aster-like to spindle-like structures. The complex consists of two characterized MAPs (TPX2, XMAP215), a plus end-directed motor (Eg5), a mitotic kinase (Aurora A), and HURP, a protein associated with hepatocellular carcinoma. Formation and function of the complex is dependent on Aurora A activity. HURP protein was further characterized and shown to bind microtubules and affect their organization both in vitro and in vivo. In egg extract, anti-HURP antibodies disrupt the formation of both Ran-dependent and chromatin and centrosome-induced spindles. HURP is also required for the proper formation and function of mitotic spindles in HeLa cells.
HURP is a new and essential component of the mitotic apparatus. HURP acts as part of a multicomponent complex that affects the growth or stability of spindle MTs and is required for spindle MT organization.
在非洲爪蟾卵提取物中，结合鸟苷三磷酸（GTP）的Ran可诱导微管组装成星状体和纺锤体样结构。微管相关蛋白（MAP）TPX2可介导Ran在星状体形成中的作用，但尚未明确负责从星状体样结构转变为纺锤体样结构的因子。
在此，我们鉴定出一种对于从星状体样结构转变为纺锤体样结构所必需的复合体。该复合体由两种已明确的MAP（TPX2、XMAP215）、一种正端定向马达蛋白（驱动蛋白Eg5）、一种有丝分裂激酶（极光激酶A）以及与肝细胞癌相关的蛋白HURP组成。该复合体的形成和功能依赖于极光激酶A的活性。我们对HURP蛋白进行了进一步表征，结果显示其在体外和体内均可结合微管并影响微管的组织。在卵提取物中，抗HURP抗体可破坏Ran依赖型以及染色质和中心体诱导型纺锤体的形成。HURP对于HeLa细胞中有丝分裂纺锤体的正常形成和功能也是必需的。
HURP是有丝分裂装置的一个新的必需组分组成。HURP作为一个多组分复合体的一部分发挥作用，该复合体影响纺锤体微管的生长或稳定性，并且是纺锤体微管组织所必需的。
