Kinetochores moving away from their associated pole do not exert a significant pushing force on the chromosome
Kinetochores moving away from their associated pole do not exert a significant pushing force on the chromosome
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DOI：
10.1083/jcb.135.2.315
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发表时间：
1996-10-01
影响因子：
7.8
通讯作者：
Rieder, CL
中科院分区：
文献类型：
--
作者：
Khodjakov, A;Rieder, CL
我们使用视频光学显微镜和激光显微外科技术来检验这一假设，即当一个双向前中期染色体在PtK1细胞中改变位置时，着丝粒离开其相关极(AP)会对着丝粒施加推力。当我们在姐妹着丝点之间的纺锤体赤道附近快速切断国会染色体时，最初“引导”向极(P)运动的着丝点总是(17/17个细胞)继续移动P，而移动AP的“落后”着丝点总是在操作完成后立即停止移动。这个拖曳的动粒随后向最初远离50 S的极点发起运动。当我们选择性地破坏国会染色体上的前导(P移动)动粒时，也观察到了同样的结果(15/15个细胞)，该染色体距离它所离开的极点大于或等于3微米。当我们对位于极3微米内的染色体进行这项实验时，着丝粒区域要么停止移动，然后转向近极(2/4个细胞)，要么继续移动AP 30-44个S(2/4个细胞)，然后切换到P运动。最后，在PtK1纺锤体的极区产生的无着丝点的染色体片段被喷出AP，并通常以大约2微米/分钟的速度朝向纺锤体赤道。根据这些数据，我们得出结论，在移动的染色体上的动粒移动的AP不会对染色体施加显着的推力。相反，我们的结果显示，当不产生P力时，动轴处于“中性”状态，这允许它们保持静止或滑动Af，以响应足以使其K纤维伸长的外力。
We used video-light microscopy and laser microsurgery to test the hypothesis that as a bioriented prometaphase chromosome changes position in PtK1 cells, the kinetochore moving away from its associated pole (AP) exerts a pushing force on the centromere. When we rapidly severed congressing chromosomes near the spindle equator between the sister kinetochores, the kinetochore that was originally ''leading'' the motion towards a pole (P) always (17/17 cells) continued moving P whereas the ''trailing'' kinetochore moving AP always stopped moving as soon as the operation was completed. This trailing kinetochore then initiated motion towards the pole it was originally moving away from up to 50 s later. The same result was observed (15/15 cells) when we selectively destroyed the leading (P moving) kinetochore on a congressing chromosome positioned greater than or equal to 3 mu m from the pole it was moving away from. When we conducted this experiment on congressing chromosomes positioned within 3 mu m of the pole, the centromere region either stopped moving, before switching into motion towards the near pole (2/4 cells), or it continued to move AP for 30-44 s (2/4 cells) before switching into P motion. Finally, kinetochore-free chromosome fragments, generated in the polar regions of PtK1 spindles, were ejected AP and often towards the spindle equator at similar to 2 mu M/min. From these data we conclude that the kinetochore moving AP on a moving chromosome does not exert a significant pushing force on the chromosome. Instead, our results reveal that, when not generating a P force, kinetochores are in a ''neutral'' state that allows them to remain stationary or to coast Af in response to external forces sufficient to allow their K-fiber to elongate.