Human MPS1 kinase is required for mitotic arrest induced by the loss of CENP-E from kinetochores

We have determined that the previously identified dual-specificity protein kinase TrK is the human orthologue of the yeast MPS1 kinase. Yeast MPS1 (monopolar spindle) is required for spindle pole duplication and the spindle checkpoint. Consistent with the recently identified vertebrate MPS1 homologues, we found that hMPS1 is localized to centrosomes and kinetochores. In addition, hMPS1 is part of a growing list of kinetochore proteins that are localized to nuclear pores. hMPS1 is required by cells to arrest in mitosis in response to spindle defects and kinetochore defects resulting from the loss of the kinesin-like protein, CENP-E. The pattern of kinetochore localization of hMPS1 in CENP-E defective cells suggests that their interaction with the kinetochore is sensitive to microtubule occupancy rather than kinetochore tension. hMPS1 is required for MAD1, MAD2 but not hBUB1, hBUBR1 and hROD to bind to kinetochores. We localized the kinetochore targeting domain in hMPS1 and found that it can abrogate the mitotic checkpoint in a dominant negative manner. Last, hMPS1 was found to associate with the anaphase promoting complex, thus raising the possibility that its checkpoint functions extend beyond the kinetochore.

我们已经确定，先前鉴定的双特异性蛋白激酶TrK是酵母MPS1激酶的人类同源物。酵母MPS1（单极纺锤体）是纺锤体极复制和纺锤体检查点所必需的。与最近鉴定的脊椎动物MPS1同源物一致，我们发现人MPS1（hMPS1）定位于中心体和动粒。此外，hMPS1是越来越多定位于核孔的动粒蛋白中的一员。细胞需要hMPS1在有丝分裂中因纺锤体缺陷以及由于驱动蛋白样蛋白CENP - E缺失导致的动粒缺陷而停滞。在CENP - E缺陷细胞中hMPS1在动粒的定位模式表明，它们与动粒的相互作用对微管占据敏感，而非对动粒张力敏感。hMPS1是MAD1、MAD2结合到动粒所必需的，但不是hBUB1、hBUBR1和hROD结合到动粒所必需的。我们定位了hMPS1中的动粒靶向结构域，并发现它可以以显性负性方式废除有丝分裂检查点。最后，发现hMPS1与后期促进复合物相关联，从而增加了其检查点功能延伸超出动粒的可能性。