Peters Nick T, Kropf Darryl L
Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
BMC Plant Biol. 2006 Aug 31;6:19. doi: 10.1186/1471-2229-6-19.
Monastrol, a chemical inhibitor specific to the Kinesin-5 family of motor proteins, was used to examine the functional roles of Kinesin-5 proteins during the first, asymmetric cell division cycle in the brown alga Silvetia compressa.
Monastrol treatment had no effect on developing zygotes prior to entry into mitosis. After mitosis entry, monastrol treatment led to formation of monasters and cell cycle arrest in a dose dependent fashion. These findings indicate that Kinesin-5 motors maintain spindle bipolarity, and are consistent with reports in animal cells. At low drug concentrations that permitted cell division, spindle position was highly displaced from normal, resulting in abnormal division planes. Strikingly, application of monastrol also led to formation of numerous cytasters throughout the cytoplasm and multipolar spindles, uncovering a novel effect of monastrol treatment not observed in animal cells.
We postulate that monastrol treatment causes spindle poles to break apart forming cytasters, some of which capture chromosomes and become supernumerary spindle poles. Thus, in addition to maintaining spindle bipolarity, Kinesin-5 members in S. compressa likely organize microtubules at spindle poles. To our knowledge, this is the first functional characterization of the Kinesin-5 family in stramenopiles.
莫那可林（Monastrol）是一种对驱动蛋白-5（Kinesin-5）家族运动蛋白具有特异性的化学抑制剂，用于研究在褐藻压缩银扇藻（Silvetia compressa）的第一次不对称细胞分裂周期中Kinesin-5蛋白的功能作用。
在进入有丝分裂之前，莫那可林处理对发育中的合子没有影响。进入有丝分裂后，莫那可林处理以剂量依赖的方式导致单星体的形成和细胞周期停滞。这些发现表明Kinesin-5马达维持纺锤体双极性，这与动物细胞中的报道一致。在允许细胞分裂的低药物浓度下，纺锤体位置与正常情况高度偏离，导致分裂平面异常。引人注目的是，应用莫那可林还导致在整个细胞质中形成大量的胞质星体和多极纺锤体，揭示了在动物细胞中未观察到的莫那可林处理的新效应。
我们推测莫那可林处理导致纺锤极分裂形成胞质星体，其中一些捕获染色体并成为多余的纺锤极。因此，除了维持纺锤体双极性外，压缩银扇藻中的Kinesin-5成员可能在纺锤极组织微管。据我们所知，这是在不等鞭毛类中对Kinesin-5家族的首次功能表征。
