Poleward force at the kinetochore in metaphase depends on the number of kinetochore microtubules.
Poleward force at the kinetochore in metaphase depends on the number of kinetochore microtubules.
复制标题
中期动力学上的极力取决于动型微管的数量。
DOI：
10.1083/jcb.110.2.391
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发表时间：
1990-02
影响因子：
7.8
通讯作者：
Salmon, E D
中科院分区：
文献类型：
--
作者：
Hays, T S;Salmon, E D
为了研究着丝点极向力对着丝点微管数目的依赖关系，我们用聚焦激光微束改变了减数分裂I期蝗虫精母细胞中相对同源动点的微管数目的正常平衡。用光学显微镜和电子显微镜进行观察。部分破坏一个同源动粒的辐射导致二价染色体移动到一个新的平衡位置，更接近未受辐射的动粒所在的极点；辐射剂量越大，染色体移动得越远。照射后的着丝粒上的kMT数目随照射强度的增加而减少，而未照射的着丝粒上的kMT数目保持不变，与染色体间的距离无关。假设染色体上的力在渐近平衡时是平衡的，我们的结果表明，染色体上的净向极力取决于KMT的数量和到极点的距离。相反，染色体的移动速度几乎不依赖于kMT的数量。解释着动粒上的极向力、动粒微管数量和动粒纤维长度之间关系的可能机制包括“牵引纤维模型”，其中向极力生产者沿着动粒纤维的长度分布，或者“动粒运动-极出模型”，在该模型中，位于着动粒或其附近的力生产者沿着kMT向极地拉动染色体，并对抗由极微管阵列产生的弹射力，向极增加强度。
To examine the dependence of poleward force at a kinetochore on the number of kinetochore microtubules (kMTs), we altered the normal balance in the number of microtubules at opposing homologous kinetochores in meiosis I grasshopper spermatocytes at metaphase with a focused laser microbeam. Observations were made with light and electron microscopy. Irradiations that partially damaged one homologous kinetochore caused the bivalent chromosome to shift to a new equilibrium position closer to the pole to which the unirradiated kinetochore was tethered; the greater the dose of irradiation, the farther the chromosome moved. The number of kMTs on the irradiated kinetochore decreased with severity of irradiation, while the number of kMTs on the unirradiated kinetochore remained constant and independent of chromosome-to-pole distance. Assuming a balance of forces on the chromosome at congression equilibrium, our results demonstrate that the net poleward force on a chromosome depends on the number of kMTs and the distance from the pole. In contrast, the velocity of chromosome movement showed little dependence on the number of kMTs. Possible mechanisms which explain the relationship between the poleward force at a kinetochore, the number of kinetochore microtubules, and the lengths of the kinetochore fibers at congression equilibrium include a "traction fiber model" in which poleward force producers are distributed along the length of the kinetochore fibers, or a "kinetochore motor-polar ejection model" in which force producers located at or near the kinetochore pull the chromosomes poleward along the kMTs and against an ejection force that is produced by the polar microtubule array and increases in strength toward the pole.