Cytokinesis and the contractile ring in fission yeast

The fission yeast Schizosaccharomyces pombe provides a genetic model system for the study of cytokinesis. As in many eukaryotes, cell division in fiss ion yeast requires an actin-myosin-based contractile ring. Numerous compone nts of the contractile ring that function in ring assembly, positioning and contraction have been characterized. Many of these proteins are evolutiona rily conserved, suggesting that common molecular mechanisms may govern aspe cts of eukaryotic cell division. Recent advances in the assembly and placem ent of the contractile ring are discussed. In particular, major findings ha ve been made in the characterization of myosins in cytokinesis, and in how the cell division site may be positioned by the nucleus.