The microtubule organizing centers of Schizosaccharomyces pombe

Abstract

The fission yeast Schizosaccharomyces pombe ( S. pombe ) is assuming a higher profile in the study of diverse aspects of microtubule function during mitosis and in cellular morphogenesis. The study of S. pombe makes a major contribution to the understanding of how microtubules can control morphogenesis. The radical differences in the cell cycle organization, morphology, and great evolutionary distance that distinguish S. pombe from the most intensively studied model eukaryote, Saccharomyces cerevisiae ( S. cerevisiae ) , are discussed in the chapter. The formation of discrete microtubule organizing centers (MTOC) at distinct stages of the life cycle offers an attractive system for the study of de novo MTOC formation. The lack of any clear S. cerevisiae homologs for two of the handful of essential components of the S. pombe spindle pole body (SPB) that are identified suggests that S. pombe may reveal much about the degree of conservation of MTOC function between species. There are three distinct MTOC in S. pombe: (1) the SPB, which is present throughout the entire life cycle, (2) the equatorial MTOC (EMTOC), which forms at the end of mitosis at the site of cell division, and (3) the tip-associated MTOC (TAM), which forms at the cell tip during mating. Thus, the system offers many insights into the molecular basis of microtubule nucleation and lends itself to the study of de novo MTOC formation.