9 Mitosis and Cytokinesis in the Fission Yeast, Schizosaccharomyces pombe

Abstract

I. INTRODUCTION
Schizosaccharomyces pombe cells are rod-shaped with round capped ends (see Fig. 2). They have a uniform diameter of about 3.5 μm and grow by extension at both ends with a length ranging from 7 μm to 16 μm (Mitchison 1970; Miyata et al. 1978). Whereas the yeast Saccharomyces cerevisiae cells divide by budding, S. pombe cells divide by fission. S. pombe cells are more stable as a haploid than as a diploid. Although diploid zygotes can arise through conjugation of two haploid cells, diploid cells tend to undergo an immediate meiosis to form haploid spores. Under favorable conditions, fission yeast reproduce asexually through the mitotic cell cycle. Typical of all eukaryotic cells, the cell cycle is composed of discrete G₁, S, G₂, and M phases (pre-DNA synthesis, DNA synthesis, post-DNA synthesis, and mitotic phases, respectively). Among the various phases, the events in the mitotic phase are the most dramatic and most striking. Replicated DNAs become precisely separated into two daughter nuclei during mitosis. Cytokinesis then divides the cell equally into two daughter cells each with identical genetic materials. The aim of this chapter is to describe the critical events that occur in mitosis and the gene products that are known to affect these events in the yeast S. pombe. Gene products that control the final septation and cell separation events following mitosis are also discussed (for review, see Fankhauser and Simanis 1994b).

Although both S. pombe and S. cerevisiae are ideal for laboratory investigations and serve as excellent...