CaMtw1, a Member of the Evolutionarily Conserved Mis12 Kinetochore Protein Family, is Required for Efficient Inner Kinetochore Assembly in the Pathogenic Yeast Candida Albicans

Proper assembly of the kinetochore, a multi-protein complex that mediates attachment of centromere DNA to spindle microtubules on each chromosome, is required for faithful chromosome segregation. Each previously characterized member of the Mis12/Mtw1 protein family is part of an essential subcomplex in the kinetochore. In this work, we identify and characterize CaMTW1, which encodes the homologue of the human Mis12 protein in the pathogenic budding yeast Candida albicans. Subcellular localization and chromatin immunoprecipitation assays confirmed CaMtw1 is a kinetochore protein. CaMtw1 is essential for viability. CaMtw1-depleted cells and cells in which CaMtw1 was inactivated with a temperature-sensitive mutation had reduced viability, accumulated at the G2/M stage of the cell cycle, and exhibited increased chromosome missegregation. CaMtw1 depletion also affected spindle length and alignment. Interestingly, in C. albicans, CaMtw1 and the centromeric histone, CaCse4, influence each other for kinetochore localization. In addition, CaMtw1 is required for efficient kinetochore recruitment of another inner kinetochore protein, the CENP-C homologue, CaMif2. Mis12/Mtw1 proteins have well-established roles in the recruitment and maintenance of outer kinetochore proteins. We propose that Mis12/Mtw1 proteins also have important co-dependent interactions with inner kinetochore proteins and that these interactions may increase the fidelity of kinetochore formation.