Kinetochore Components Required for Centromeric Chromatin Assembly Are Impacted by Msc1 in Schizosaccharomyces pombe

Abstract

Eukaryotic chromosome segregation requires a protein complex known as the kinetochore that mediates attachment between mitotic spindle microtubules and centromere-specific nucleosomes composed of the widely conserved histone variant CENP-A. Mutations in kinetochore proteins of the fission yeast lead to chromosome missegregation such that daughter cells emerge from mitosis with unequal DNA content. We find that multiple copies of Msc1-a fission yeast homolog of the KDM5 family of proteins-suppresses the temperature-sensitive growth defect of several kinetochore mutants, including and , as well as, , and, components of the Constitutive Centromere Associated Network (CCAN). On the other hand, deletion of exacerbates both the growth defect and chromosome missegregation phenotype of each of these mutants. The C-terminal PHD domains of Msc1, previously shown to associate with a histone deacetylase activity, are necessary for Msc1 function when kinetochore mutants are compromised. We also demonstrate that, in the absence of Msc1, the frequency of localization to the kinetochore of Mis16 and Mis15 is altered from wild-type cells. As we show here for, others have shown that elevating levels acts similarly to promote survival of the CCAN mutants. The rescue of and by is, however, independent of Thus, Msc1 appears to contribute to the chromatin environment at the centromere: the absence of Msc1 sensitizes cells to perturbations in kinetochore function, while elevating Msc1 overcomes loss of function of critical components of the kinetochore and centromere.

Swr1 mediated H2A.ZPht1 incorporation designates centromere DNA for de novo CENP-ACnp1 assembly

“…Defective chromosome segregation is observed in several eukaryotes with aberrant H2A.Z deposition and has been attributed to impaired centromeric cohesion resulting from improper heterochromatin formation (Boyarchuk et al, 2011). Notably, loss of S. pombe H2A.Z Pht1 or Swr1C-associated Msc1 is synthetically lethal with mutations in CENP-A Cnp1 and its loading factors and Msc1 overexpression rescues these lethal mutations (Ahmed et al, 2007;Gao et al, 2017;Kim et al, 2009). Such genetic interactions underscore a role for H2A.Z Pht1 in CENP-A Cnp1 deposition, kinetochore integrity and chromosome segregation.…”

“…Msc1 is a KDM5-related protein that associates with S. pombe Swr1C but is absent in S. cerevisiae. Msc1 has also been implicated in H2A.Z Pht1 deposition and contributes to genome stability (Ahmed et al, 2007;Buchanan et al, 2009;Gao et al, 2017;Hou et al, 2010). Since H2A.Z Pht1 -myc was measurably enriched within the central domain of centromere we next applied qChIP and ChIP-seq to determine if Swr1 and Msc1 also associate with the central domain.…”