Abstract
Chromosome segregation during cell division requires engagement of kinetochores of sister chromatids with microtubules emanating from opposite poles. As the corresponding microtubules shorten, these 'bioriented' sister kinetochores experience tension-dependent stabilization of microtubule attachments. The yeast XMAP215 family member and microtubule polymerase, Stu2, associates with kinetochores and contributes to tension-dependent stabilization in vitro. We show here that a C-terminal segment of Stu2 binds the four-way junction of the Ndc80 complex (Ndc80c) and that residues conserved both in yeast Stu2 orthologs and in their metazoan counterparts make specific contacts with Ndc80 and Spc24. Mutations that perturb this interaction prevent association of Stu2 with kinetochores, impair cell viability, produce biorientation defects, and delay cell cycle progression. Ectopic tethering of the mutant Stu2 species to the Ndc80c junction restores wild-type function in vivo. These findings show that the role of Stu2 in tension-sensing depends on its association with kinetochores by binding with Ndc80c.
Highlights
Equal partitioning of duplicated chromosomes during cell division preserves integrity of the genome in each of the two daughter cells
We found that Stu2 binds Ndc80cdwarf as efficiently as it does full-length Ndc80 complex (Ndc80c) (Figure 1B)
We found that a segment at the C-terminus of Stu2, most of which is conserved among budding and fission yeast and referred to here as the ‘C-terminal segment (CTS)’ (Figure 1A), is required for binding Ndc80c
Summary
Equal partitioning of duplicated chromosomes during cell division preserves integrity of the genome in each of the two daughter cells. The Aurora B kinase (Ipl in budding yeast) is the immediate agent of error correction (Biggins and Murray, 2001; Biggins et al, 1999; Cheeseman et al, 2002; DeLuca et al, 2006; Hauf et al, 2003; Tanaka et al, 2002). In the absence of tension, Ipl phosphorylates Ndc (DeLuca et al, 2006; Hauf et al, 2003), an essential part of the microtubule-contacting apparatus of a yeast kinetochore, and several other kinetochore substrates, including critical targets within the Dam complex (Biggins et al, 1999; Cheeseman et al, 2002; Kang et al, 2001).
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