Directional instability of kinetochore motility during chromosome congression and segregation in mitotic newt lung cells: a push-pull mechanism.
Directional instability of kinetochore motility during chromosome congression and segregation in mitotic newt lung cells: a push-pull mechanism.
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DOI：
10.1083/jcb.122.4.859
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发表时间：
1993-08
期刊：
影响因子：
--
通讯作者：
Salmon ED
中科院分区：
文献类型：
--
作者：
Skibbens RV;Skeen VP;Salmon ED
大多数有丝分裂大会和分离模型假设着丝粒处仅发生极向拉力。然而，有报道称，对于几种不同的细胞类型，单向和双向染色体在整个有丝分裂过程中都会向极点或远离极点振荡。我们使用高分辨率视频显微镜和计算机辅助跟踪技术的新方法来测量活蝾螈肺细胞有丝分裂期间各个动粒相对于其极点随时间的位置。结果表明，当着丝粒通过附着到着丝粒微管（kMT）的正端而被拴在纺锤体极上时，它们在整个有丝分裂过程中振荡。振荡不是正弦的。相反，动粒突然（快至 6 秒或更短）在持续（平均持续时间约 1.5 分钟）向极点 (P) 和远离极点 (AP) 运动的阶段之间切换。这种动粒“方向不稳定性”是 kMT 正端运动的一种特性，因为先前观察到 kMT 晶格上的荧光标记仅表现出相对较慢的 P 运动。每个 P 相和 AP 相均由一个或几个等速域（平均速度约为 1.7 微米/分钟）组成。从前期到后期中期，P 期和 AP 期的速度相似。着丝粒偶尔会切换到无运动或混乱运动的不确定 (N) 阶段，与 P 和 AP 阶段的持续时间相比，该阶段通常很短暂。在向赤道会聚期间或在后期向极地运动期间发生的净染色体位移主要是由持续时间的差异产生的，而不是由 P 和 AP 运动的速度产生的。仔细分析着丝粒变形表明，着丝粒P运动产生拉力，而着丝粒AP运动产生推力。这些数据表明着丝粒方向不稳定性是染色体会聚和分离过程的基础。我们认为着丝粒附着位点的张力是控制着丝粒运动的 P 阶段和 AP 阶段之间切换的关键因素。
Most models of mitotic congression and segregation assume that only poleward pulling forces occur at kinetochores. However, there are reports for several different cell types that both mono-oriented and bi- oriented chromosomes oscillate toward and away from the pole throughout mitosis. We used new methods of high resolution video microscopy and computer-assisted tracking techniques to measure the positions over time of individual kinetochores with respect to their poles during mitosis in living newt lung cells. The results show that kinetochores oscillate throughout mitosis when they are tethered to spindle poles by attachment to the plus-ends of kinetochore microtubules (kMTs). Oscillations were not sinusoidal. Instead, kinetochores abruptly (as quick as 6 s or less) switched between persistent (approximately 1.5 min average duration) phases of poleward (P) and away from the pole (AP) movement. This kinetochore "directional instability" was a property of motility at the plus-ends of kMTs since fluorescent marks on the lattice of kMTs have previously been observed to exhibit only relatively slow P movement. Each P and AP phase consisted of one or a few constant velocity domains (approximately 1.7 microns/min average velocity). Velocities of P and AP phases were similar from prometaphase through mid-anaphase. Kinetochores occasionally switched to an indeterminant (N) phase of no or confused motion, which was usually brief compared to the durations of P and AP phases. Net chromosome displacements that occurred during congression to the equator or poleward movement during anaphase were primarily generated by differences in the durations and not the velocities of P and AP movements. Careful analysis of centromere deformation showed that kinetochore P movement produced pulling forces while kinetochore AP movement produced pushing forces. These data show that kinetochore directional instability is fundamental to the processes of chromosome congression and segregation. We argue that tension at the kinetochore attachment site is a key factor which controls the switching between P and AP phases of kinetochore motion.