ISOLATION AND CHARACTERIZATION OF A GENE (CBF2) SPECIFYING A PROTEIN-COMPONENT OF THE BUDDING YEAST KINETOCHORE

We have cloned and determined the nucleotide sequence of the gene (CBF 2) specifying the large (110 kD) subunit of the 240-kD multisubunit ye ast centromere binding factor CBF3, which binds selectively in vitro t o yeast centromere DNA and contains a minus end-directed microtubule m otor activity. The deduced amino acid sequence of CBF2p shows no seque nce homologies with known molecular motors, although a consensus nucle otide binding site is present. The CBF2 gene is essential for viabilit y of yeast and is identical to NDC10, in which a conditional mutation leads to a defect in chromosome segregation (Goh, P.-Y., and J. V. Kil martin, in this issue of The Journal of Cell Biology). The combined in vitro and in vivo evidence indicate that CBF2p is a key component of the budding yeast kinetochore.