期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：41
页码：E5583-E5589
DOI：10.1073/pnas.1513882112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceDuring cell division, multisubunit kinetochores partition chromosomes while maintaining a grip on dynamic microtubules under tension. Previous work in Caenorhabditis elegans showed that the central kinetochore component, Mis12/MIND (Mtw1, Nsl1, Nnf1, Dsn1) complex, increases microtubule binding of outer kinetochore complexes, but the mechanism for this enhancement remains unknown. Here, we identify new contacts between MIND and the outer kinetochore Ndc80 (Ndc80, Nuf2, Spc24, Spc25) complex that are essential for interaction in vitro and for cell viability. Using single-molecule microscopy, we demonstrate that a single MIND complex enhances the microtubule binding of a single Ndc80 complex. Our results suggest a molecular mechanism for enhancing kinetochore-microtubule attachment by a central kinetochore component. Multiple protein subcomplexes of the kinetochore cooperate as a cohesive molecular unit that forms load-bearing microtubule attachments that drive mitotic chromosome movements. There is intriguing evidence suggesting that central kinetochore components influence kinetochore-microtubule attachment, but the mechanism remains unclear. Here, we find that the conserved Mis12/MIND (Mtw1, Nsl1, Nnf1, Dsn1) and Ndc80 (Ndc80, Nuf2, Spc24, Spc25) complexes are connected by an extensive network of contacts, each essential for viability in cells, and collectively able to withstand substantial tensile load. Using a single-molecule approach, we demonstrate that an individual MIND complex enhances the microtubule-binding affinity of a single Ndc80 complex by fourfold. MIND itself does not bind microtubules. Instead, MIND binds Ndc80 complex far from the microtubule-binding domain and confers increased microtubule interaction of the complex. In addition, MIND activation is redundant with the effects of a mutation in Ndc80 that might alter its ability to adopt a folded conformation. Together, our results suggest a previously unidentified mechanism for regulating microtubule binding of an outer kinetochore component by a central kinetochore complex.
