Ctf19p: A novel kinetochore protein in Saccharomyces cerevisiae and a potential link between the kinetochore and mitotic spindle

A genetic synthetic dosage lethality (SDL) screen using CTF13 encoding a kn own kinetochore protein as the overexpressed reference gene identified two chromosome transmission fidelity (ctf) mutants, YCTF58 and YCTF26, These mu tant strains carry independent alleles of a novel gene, which we have desig nated CTF19. In light of its potential role in kinetochore function, we hav e cloned and characterized the CTF19 gene in detail. CTF19 encodes a noness ential 369-amino acid protein. cgf19 mutant strains display a severe chromo some missegregation phenotype, are hypersensitive to benomyl, and accumulat e at G2/M in cycling cells. CTF19 genetically interacts with kinetochore st ructural mutants and mitotic checkpoint mutants. In addition, ctf19 mutants show a defect in the ability of centromeres on minichromosomes to bind mic rotubules in an in vitro assay. In vivo cross-linking and chromatin immunop recipitation demonstrates that Ctf19p specifically interacts with CEN DNA, Furthermore, Ctf19-HAp localizes to the nuclear face of the spindle pole bo dy and genetically interacts with a spindle-associated protein. We propose that Ctf19p is part of a macromolecular kinetochore complex, which may func tion as a link between the kinetochore and the mitotic spindle.