Role of kinetochore stretching in controlling the spindle-assembly checkpoint

染色体的忠实分离依赖于纺锤体组装检查点(SAC)，它推迟后期的开始，直到所有的动粒都附着在微管(MT)上。SAC监测运动中枢的MT依恋，但它是否也感觉到“紧张”的存在，长期以来一直是一个有争议的问题。我们发现，施加在姐妹着丝点上的“张力”是可有可无的，但伸展着丝点是抑制SAC所必需的(Uchida等，2009)。因此，研究“张力”是否导致动粒伸展是至关重要的。我们通过设计微管附着在动粒上但不受拉力的条件，从实验上解决了这个问题。在此条件下，我们发现运动中枢在MT附着时发生了伸展。这些结果表明，完整的动粒拉力不是动粒拉伸所必需的，因此挑战了SAC直接监测张力存在的观点。

Faithful segregation of chromosomes relies on the spindle-assembly checkpoint(SAC), which delays anaphase onset until all kinetochores are attached to microtubules(MT). The SAC monitors MT attachment at kinetochores, but whether it also senses the presence of 'tension' has long been a matter of debate. We found that 'tension' applied across sister kinetochores, which stretches centromeres, is dispensable, but stretching of kinetochores is required for silencing the SAC(Uchida et al., 2009). It is therefore crucial to investigate if 'tension' underlies kinetochore stretching. We addressed this question experimentally by engineering the conditions that microtubules are attached to kinetochors but free from the pulling force. Under these conditions, we found that kinetochores underwent stretching upon MT attachment. These results suggest that intact kinetochore-pulling force is not required for kinetochore stretching, thus challenging the notion that SAC directly monitors the presence of tension.