Distinct Organization and Regulation of the Outer Kinetochore KMN Network Downstream of CENP-C and CENP-T
Author(s)Rago, Florencia; Gascoigne, Karen E.; Cheeseman, Iain M
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The kinetochore provides a vital connection between chromosomes and spindle microtubules [1 and 2]. Defining the molecular architecture of the core kinetochore components is critical for understanding the mechanisms by which the kinetochore directs chromosome segregation. The KNL1/Mis12 complex/Ndc80 complex (KMN) network acts as the primary microtubule-binding interface at kinetochores  and provides a platform to recruit regulatory proteins . Recent work found that the inner kinetochore components CENP-C and CENP-T act in parallel to recruit the KMN network to kinetochores [5, 6, 7 and 8]. However, due to the presence of these dual pathways, it has not been possible to distinguish differences in the nature of kinetochore assembly downstream of CENP-C or CENP-T. Here, we separated these pathways by targeting CENP-C and CENP-T independently to an ectopic chromosomal locus in human cells. Our work reveals that the organization of the KMN network components downstream of CENP-C and CENP-T is distinct. CENP-C recruits the Ndc80 complex through its interactions with KNL1 and the Mis12 complex. In contrast, CENP-T directly interacts with Ndc80, which in turn promotes KNL1/Mis12 complex recruitment through a separate region on CENP-T, resulting in functional relationships for KMN network localization that are inverted relative to the CENP-C pathway. We also find that distinct regulatory paradigms control the assembly of these pathways, with Aurora B kinase promoting KMN network recruitment to CENP-C and cyclin-dependent kinase (CDK) regulating KMN network recruitment to CENP-T. This work reveals unexpected complexity for the architecture and regulation of the core components of the kinetochore-microtubule interface.
DepartmentMassachusetts Institute of Technology. Department of Biology; Whitehead Institute for Biomedical Research
Rago, Florencia, Karen E. Gascoigne, and Iain M. Cheeseman. “Distinct Organization and Regulation of the Outer Kinetochore KMN Network Downstream of CENP-C and CENP-T.” Current Biology 25.5 (2015): 671–677.
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