Twenty Ways of Looking at a Centrosome

Any serious understanding of how centrosomes work will depend on having a complete parts list and knowledge of how the parts fit together. One of the big suc-The Centrosome in Cell Replication cesses for assembling this parts list was the identifica-and Early Development tion of ␥-tubulin and the realization of its key role in Edited by R.E. Palazzo and G.P. Schatten microtubule nucleation. ␥-tubulin is a distinct tubulin San Diego, CA: Academic Press (2000). 470 pp. $129.95 found in the PCM and on the outer surfaces of the SPB. Two chapters describe genetic studies on ␥-tubulin. Although these experiments nicely support the notion that Most cell biologists would admit that the centrosome ␥-tubulin nucleates microtubules, they highlight aspects has an ineffable quality. Discovered at the end of the of ␥-tubulin function that are less well understood. nineteenth century, it was dubbed the " dynamic center For example, although ␥-tubulin interacts with ␣-tubulin of the cell " and considered to hold the keys to under-in polymerized microtubules, the genetic data raises standing mitosis, fertilization, morphogenesis, and can-the possibility that ␥-tubulin might also interact with cer. It is easy to see why the centrosome seemed to ␤-tubulin at some point during the assembly process. promise a direct route to the essence of these problems. Another excellent chapter reviews the biochemical Like the chromosomes, the centrosome is duplicated properties of ␥-tubulin. This includes the partitioning of once each cell division, and the heart of the centrosome, ␥-tubulin into different complexes (one of which is the the centriole, is duplicated with new elements formed ␥-tubulin ring complex found at the centrosome), and a adjacent to and in strict geometric relation to old ones. discussion of the two radically different models pro-Puzzling out this intriguing pattern of replication has posed to explain the role of ␥-tubulin in microtubule been a significant challenge, generating much writing nucleation. The next step in building the centrosome wiring dia-about the " mystery " of the centrosome. In recent years, gram is to define how the nucleating activity is integrated there has been progress in the molecular characteriza-into the general structure of centrosomes. Two chapters tion of the centrosome which has lifted many mysteries lay out how far along this effort has advanced for the but also lead to some new ones. Thus, after more than budding yeast SPB. In budding yeast, most if not all of 100 years of …