The spindle checkpoint of the yeast Saccharomyces cerevisiae requires kinetochore function and maps to the CBF3 domain

We have measured the activity of the spindle checkpoint in null mutants lac king kinetochore activity in the yeast Saccharomyces cerevisiae. We constru cted deletion mutants for nonessential genes br one-step gene replacements. We constructed heterozygous deletions of one copy of essential genes in di ploid cells and purified spores containing the deletion allele. In addition , we made gene fusions for three essential genes to target the encoded prot eins for proteolysis (degron alleles).We determined that Ndc10p, Ctf13p, an d Cep3p are required for checkpoint activity. In contrast, cells lacking Cb f1p, Ctf19p, Mcm21p, Slk19p, Cse4p, Mif2p, Mck1p, and Kar3p are checkpoint proficient. We conclude that the kinetochore play a critical role in checkp oint signaling in S. cerevisiae. Spindle checkpoint activity maps to a disc reet domain within the kinetochore and depends on the CBF3 protein complex.