Histone H3-like variant which exclusively replaces conventional H3 in the nucleosome core of centromeric chromatin at the inner plate of the kinetochore. Required for recruitment and assembly of kinetochore proteins, mitotic progression and chromosome segregation. May serve as an epigenetic mark that propagates centromere identity through replication and cell division. Component of the core kinetochore. Interacts with mis6 and sim4. Localizes exclusively in the kinetochore domain of centromeres. Ubiquitinated. Is degraded through ubiquitin mediated proteolysis when not protected by its association to the kinetochore. This may ensure exclusive localization of cnp1 to the kinetochore. Belongs to the histone H3 family.