The peroxisome: a production in four acts

A cell regulates the number, size, and kind of each organelle it possesses in response to its particular role in an environment or tissue. Yet we still know little about how the molecular signaling networks within each cell perform such regulation. In this issue, Saleem et al. (Saleem, R. A., B. Knoblach, F. D. Mast, J. J. Smith, J. Boyle, C. M. Dobson, R. Long-O'Donnell, R. A. Rachubinski, and J. D. Aitchison. 2008. J. Cell Biol. 181: 281-292) show for the first time how groups of kinases and phosphatases are organized to control when and how a cell assembles one kind of organelle, the peroxisome.