The CENP-A N-Tail Confers Epigenetic Stability to Centromeres via the CENP-T Branch of the CCAN in Fission Yeast

In most eukaryotes, centromeres are defined epigenetically by presence of the histone H3 variant CENP-A [1–3]. CENP-A-containing chromatin recruits the constitutive centromere-associated network (CCAN) of proteins, which in turn directs assembly of the outer kinetochore to form microtubule attachments and ensure chromosome segregation fidelity [4–6]. Whereas the mechanisms that load CENP-A at centromeres are being elucidated, the functions of its divergent N-terminal tail remain enigmatic [7–12]. Here, we employ the well-studied fission yeast centromere [13–16] to investigate the function of the CENP-A (Cnp1) N-tail. We show that alteration of the N-tail does not affect Cnp1 loading at centromeres, outer kinetochore formation, or spindle checkpoint signaling but nevertheless elevates chromosome loss. N-tail mutants exhibited synthetic lethality with an altered centromeric DNA sequence, with rare survivors harboring chromosomal fusions in which the altered centromere was epigenetically inactivated. Elevated centromere inactivation was also observed for N-tail mutants with unaltered centromeric DNA sequences. N-tail mutants specifically reduced localization of the CCAN proteins Cnp20/CENP-T and Mis6/CENP-I, but not Cnp3/CENP-C. Overexpression of Cnp20/CENP-T suppressed defects in an N-tail mutant, suggesting a link between reduced CENP-T recruitment and the observed centromere inactivation phenotype. Thus, the Cnp1 N-tail promotes epigenetic stability of centromeres in fission yeast, at least in part via recruitment of the CENP-T branch of the CCAN. •Cnp1/CENP-A N-tail mutants are viable but exhibit elevated chromosome loss•N-tail mutants do not perturb Cnp1 loading or outer kinetochore assembly•N-tail mutants exhibit centromere inactivation enhanced by an altered centromere•N-tail mutants reduce the centromere levels of the CENP-T branch of the CCAN Folco et al. show that the N-terminal tail of the centromeric histone variant Cnp1/CENP-A in fission yeast protects against centromere inactivation and chromosome loss. They link this epigenetic protection function to a role for the N-tail in targeting the CENP-T branch of the constitutive centromere-associated network to centromeres.