Principal Investigator Frank Solomon
A second element of the structure-function analysis of tubulin is based on another cold-sensitive beta-tubulin allele, tub1-729. This mutant also arrests with no microtubules, like tub1-724. However, the defect in the Tub1-729p is at the attachment between microtubules and the kinetochores. The tub1-729 phenotype is suppressed by overexpression only of a subset of the mitotic checkpoint genes, a fact that distinguishes among their activities. In addition, that suppression does not require downstream elements of the checkpoint pathway. The results demonstrate a structural role for products of some checkpoint genes, and suggest a genetic tool to analyze the details of microtubule-kinetochore attachment.
Prospects: These analyses of cellular regulation of tubulin reveal important quantitative and qualitative regulation that can not be recapitulated by in vitro approaches.
The next goals are to identify the mechanisms by which cells regulate tubulin expression; to characterize the earliest steps in microtubule morphogenesis, those that lead to heterodimer formation; to pursue a structure-function analysis of the tubulins; and to understand the mechanism of beta-tubulin lethality.