Rieder C L, Davison E A, Jensen L C, Cassimeris L, Salmon E D
J Cell Biol. 1986 Aug;103(2):581-91. doi: 10.1083/jcb.103.2.581.
During mitosis a monooriented chromosome oscillates toward and away from its associated spindle pole and may be positioned many micrometers from the pole at the time of anaphase. We tested the hypothesis of Pickett-Heaps et al. (Pickett-Heaps, J. D., D. H. Tippit, and K. R. Porter, 1982, Cell, 29:729-744) that this behavior is generated by the sister kinetochores of a chromosome interacting with, and moving in opposite direction along, the same set of polar microtubules. When the sister chromatids of a monooriented chromosome split at the onset of anaphase in newt lung cells, the proximal chromatid remains stationary or moves closer to the pole, with the kinetochore leading. During this time the distal chromatid moves a variable distance radially away from the pole, with one or both chromatid arms leading. Subsequent electron microscopy of these cells revealed that the kinetochore on the distal chromatid is free of microtubules. These results suggest that the distal kinetochore is not involved in the positioning of a monooriented chromosome relative to the spindle pole or in its oscillatory movements. To test this conclusion we used laser microsurgery to create monooriented chromosomes containing one kinetochore. Correlative light and electron microscopy revealed that chromosomes containing one kinetochore continue to undergo normal oscillations. Additional observations on normal and laser-irradiated monooriented chromosomes indicated that the chromosome does not change shape, and that the kinetochore region is not deformed, during movement away from the pole. Thus movement away from the pole during an oscillation does not appear to arise from a push generated by the single pole-facing kinetochore fiber, as postulated (Bajer, A. S., 1982, J. Cell Biol., 93:33-48). When the chromatid arms of a monooriented chromosome are cut free of the kinetochore, they are immediately ejected radially outward from the spindle pole at a constant velocity of 2 micron/min. This ejection velocity is similar to that of the outward movement of an oscillating chromosome. We conclude that the oscillations of a monooriented chromosome and its position relative to the spindle pole result from an imbalance between poleward pulling forces acting at the proximal kinetochore and an ejection force acting along the chromosome, which is generated within the aster and half-spindle.
在有丝分裂过程中，单极定向染色体朝着并远离与其相连的纺锤体极振荡，在后期时可能位于距纺锤体极数微米远的位置。我们检验了皮克特 - 希普斯等人（皮克特 - 希普斯，J. D.，D. H. 蒂皮特，和 K. R. 波特，1982 年，《细胞》，29:729 - 744）提出的假说，即这种行为是由染色体的姐妹动粒与同一组极微管相互作用并沿相反方向移动所产生的。当蝾螈肺细胞中一个单极定向染色体的姐妹染色单体在后期开始时分开时，近端染色单体保持静止或向极移动得更近，动粒在前。在此期间，远端染色单体沿径向从极移动可变距离，一条或两条染色单体臂在前。随后对这些细胞的电子显微镜观察显示，远端染色单体上的动粒没有微管。这些结果表明，远端动粒不参与单极定向染色体相对于纺锤体极的定位或其振荡运动。为了验证这一结论，我们使用激光显微手术创建了含有一个动粒的单极定向染色体。相关的光镜和电镜观察表明，含有一个动粒的染色体继续进行正常振荡。对正常和激光照射的单极定向染色体的进一步观察表明，染色体在远离极的运动过程中形状不变，动粒区域也没有变形。因此，振荡过程中远离极的运动似乎并非如所假设的那样（巴耶尔，A. S.，1982 年，《细胞生物学杂志》，93:33 - 48）由单个面向极的动粒纤维产生的推力引起。当一个单极定向染色体的染色单体臂从动粒处切断时，它们会以 2 微米/分钟的恒定速度立即从纺锤体极沿径向向外弹出。这种弹出速度与振荡染色体向外移动的速度相似。我们得出结论，单极定向染色体的振荡及其相对于纺锤体极的位置是由近端动粒处的向极拉力与沿染色体作用的弹出力之间的不平衡导致的，该弹出力在星体和半纺锤体内产生。
