Mutants of the Drosophila ncd microtubule motor protein cause centrosomal and spindle pole defects in mitosis.
Mutants of the Drosophila ncd microtubule motor protein cause centrosomal and spindle pole defects in mitosis.
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发表时间：
1994-04
影响因子：
4
通讯作者：
S. Endow;Rashmi Chandra;D. J. Komma;Akihiko H. Yamamoto;Edward D. Salmon
中科院分区：
文献类型：
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作者：
S. Endow;Rashmi Chandra;D. J. Komma;Akihiko H. Yamamoto;Edward D. Salmon
非红细胞分离蛋白（nonclaretdisjunctional，ncd）是果蝇减数分裂和有丝分裂早期染色体分布所必需的一种微管运动蛋白。NCD在微管上以与驱动蛋白相反的极性向微管负末端移位，并且与染色体/纺锤体制备物中的纺锤体相关。在这里，我们报告了一个新的突变体的ncd所造成的部分删除预测卷曲螺旋中央柄。突变体蛋白质表现出的易位速度和能力，以产生扭矩的运动性测定接近全长ncd，但只有部分拯救染色体错误分离的无效突变。抗体染色实验表明，部分缺失突变体和无效突变体导致中心体和纺锤体极缺陷，包括中心体分裂和中心体从纺锤体极缺失，并将ncd定位于野生型胚胎的中心体和纺锤体。ncd与纺锤体和中心体的关联是微管和细胞周期依赖的：用秋水仙素抑制微管组装可以消除ncd染色，在前中期，中期和后期观察到中心体染色，但在后期/末期减少。中心体染色的细胞周期依赖性和突变体的缺陷为有丝分裂中纺锤体极附近或纺锤体极处的ncd马达蛋白的活性提供了明确的证据。ncd马达可能与中心体微管和纺锤体纤维相互作用，将中心体附着在纺锤体极上，并介导动粒纤维向极移位（通量），这一过程可能是有丝分裂中染色体向极移动的基础。结合之前的研究，我们的发现表明ncd在有丝分裂和减数分裂中对维持纺锤体极非常重要。
Nonclaret disjunctional (ncd) is a kinesin-related microtubule motor protein required for meiotic and early mitotic chromosome distribution in Drosophila. ncd translocates on microtubules with the opposite polarity to kinesin, toward microtubule minus ends, and is associated with spindles in chromosome/spindle preparations. Here we report a new mutant of ncd caused by partial deletion of the predicted coiled-coil central stalk. The mutant protein exhibits a velocity of translocation and ability to generate torque in motility assays comparable to near full-length ncd, but only partially rescues a null mutant for chromosome mis-segregation. Antibody staining experiments show that the partial loss-of-function and null mutants cause centrosomal and spindle pole defects, including centrosome splitting and loss of centrosomes from spindle poles, and localize ncd to centrosomes as well as spindles of wild-type embryos. Association of ncd with spindles and centrosomes is microtubule- and cell cycle-dependent: inhibition of microtubule assembly with colchicine abolishes ncd staining and centrosomal staining is observed in prometaphase, metaphase and anaphase, but diminishes in late anaphase/telophase. The cell cycle dependence of centrosomal staining and the defects of mutants provide clear evidence for activity of the ncd motor protein near or at the spindle poles in mitosis. The ncd motor may interact with centrosomal microtubules and spindle fibers to attach centrosomes to spindle poles, and mediate poleward translocation (flux) of kinetochore fibers, a process that may underlie poleward movement of chromosomes in mitosis. Together with previous work, our findings indicate that ncd is important in maintaining spindle poles in mitosis as well as in meiosis.