Saccharomyces cerevisiae

cdk2, and on cell cycle-specific proteolysis. We are working to determine the molecular mechanisms of centrosome duplication and to understand how centrosome duplication is controlled so that it happens once and only once per cell cycle. Cancer cells often have aberrant centrosome numbers, and we are investigating the relationship between aberrant centrosome number and the genome instability that is common in cancer cells. 3) Microtubule nucleation and organization. Microtubules are polymers of tubulin, which is a heterodimer of alpha-tubulin and beta-tubulin. We have identified a remarkable complex of proteins associated with a third type of tubulin, gamma-tubulin. Gamma-tubulin and its associated proteins are localized to the centrosome and are critical for initiation, or nucleation, of microtubule assembly. The gamma-tubulin complex (gammaTuRC) is a very large, ring-shaped complex and contains at least 6 proteins in addition to gamma-tubulin. We are determining the role of gamma-tubulin and its associated proteins in microtubule nucleation and organization.