Cytokinesis: Sid signals septation

Like DNA replication or chromosome segregation, cytokinesis is a once-and-only-once event in the life of a cell. What controls where, when and how a cell divides? The fission yeast Schizosaccharomyces pombe has recently become a focus for genetic studies of eukaryotic cytokinesis, and this work has revealed, among other things, a novel signal transduction pathway controlling septation [1–3]. What is remarkable about this pathway is that nearly all of its components reside in the nuclear-localized spindle pole body, the yeast equivalent of the centrosome, which Boveri [4] described one hundred years ago as “the true divisionorgan of the cell”. Papers published earlier this year from the groups of Gould [5] and McCollum [6,7] have given a further indication of how the spindle pole body becomes the headquarters for this pathway, and also how the signals generated there finally reach the division site. Interestingly, an analogous pathway also exists in the budding yeast Saccharomyces cerevisiae, although in that organism the same genetic hardware appears to control not septation per se, but rather a more general exit from mitosis [8–10].