Progress in the structural and functional characterization of kinetochores

Abstract

Kinetochores are macromolecular complexes built on a specialized chromatin domain called the centromere. Kinetochores provide a site of attachment for spindle microtubules during mitosis. They also control a cell cycle checkpoint, the spindle assembly checkpoint, which coordinates mitotic exit with the completion of chromosome alignment on the mitotic spindle. Correct kinetochore operation is therefore indispensable for accurate chromosome segregation. With multiple copies of at least 30 structural core subunits and a myriad of regulatory subunits, kinetochores are among the largest known macromolecular machines. Biochemical reconstitution and structural analysis, together with functional studies, are bringing to light the organizational principles of these complex and fascinating structures. We summarize recent work and identify a few challenges for future work.

Structure of the MIS12 Complex and Molecular Basis of Its Interaction with CENP-C at Human Kinetochores

“…Kinetochores, which are largely conserved in eukaryotes, contain ∼26 core subunits and an array of regulatory subunits (Pesenti et al., 2016). The core subunits have been classified into two distinct assemblies, designated constitutive centromere-associated network (CCAN) and Knl1 complex; Mis12 complex; Ndc80 complex (KMN), the former loosely associated with chromatin components and the latter, with spindle microtubules (McKinley and Cheeseman, 2016, Pesenti et al., 2016; Figure S1A). The 16 or more CCAN subunits fall into several discrete complexes (McKinley and Cheeseman, 2016, Pesenti et al., 2016).…”

“…The core subunits have been classified into two distinct assemblies, designated constitutive centromere-associated network (CCAN) and Knl1 complex; Mis12 complex; Ndc80 complex (KMN), the former loosely associated with chromatin components and the latter, with spindle microtubules (McKinley and Cheeseman, 2016, Pesenti et al., 2016; Figure S1A). The 16 or more CCAN subunits fall into several discrete complexes (McKinley and Cheeseman, 2016, Pesenti et al., 2016). Of these, CENP-C and the CENP-LN complex interact directly with the centromere-specific histone H3 variant CENP-A, considered the linchpin of kinetochore assembly (Carroll et al., 2009, Carroll et al., 2010, Kato et al., 2013, Weir et al., 2016).…”

Molecular basis of outer kinetochore assembly on CENP-T

“…The structural core of the kinetochore assembles from two large multi-subunit complexes, the CCAN (constitutive centromere associated network), and the KMN (KNL1 complex, MIS12 complex, NDC80 complex, abbreviated as KNL1C, MIS12C, and NDC80C), which are respectively proximal and distal to the centromeric chromatin (Pesenti et al, 2016). The affinity of the kinetochore for microtubules in the KMN is predominantly mediated by the NDC80 complex, a heterotetramer with an approximately 50 nm long coiled coil region that separates the microtubule-binding calponin homology (CH) domains of the NDC80 and NUF2 subunits from the SPC24 and SPC25 subunits (Ciferri et al, 2005; Wei et al, 2005, 2007; Ciferri et al, 2008).…”

CDK-regulated dimerization of M18BP1 on a Mis18 hexamer is necessary for CENP-A loading

“…During mitosis, chromosomes bi-orient on the mitotic spindle, a structure made of microtubules, microtubule motors, and microtubule-binding proteins (Heald and Khodjakov, 2015). Chromosomes attach to spindle microtubules through large multisubunit assemblies known as kinetochores (Pesenti et al, 2016). Besides microtubule binding, kinetochores harness a poorly understood molecular mechanism of ‘error correction’ that leads to selective stabilization of bi-oriented attachments (Foley and Kapoor, 2013).…”