Centrosome Duplication A Centriolar Pas de Deux

been stripped of most of their proteins, the pericentriolar material can be seen to consist of a fibrous core, to which other proteins and complexes are attached. Mi-crotubule nucleation is accomplished by the ␥-tubulin Stanford, California 94305 complex, a large ring-shaped multiprotein complex that localizes to the pericentriolar material and provides a template for the addition of tubulin subunits to make a The microtubule organizing center, or centrosome, is microtubule. The pericentriolar material must have spe-an unusual organelle. Unlike most organelles, it is not cific interactions with the centrioles and with functional bounded by a membrane, yet it is distinct from the sur-components, such as the ␥-tubulin complex, but these rounding cytoplasm. It is at the center of important pro-interactions have not been characterized, nor have the cesses in animal and fungal cells, yet many plant cells proteins making up the structural core of the pericentrio-completely lack it. And perhaps most perplexingly, the lar material been identified. If the pericentriolar material centrosome duplicates precisely once per cell cycle, is doing most of the heavy lifting with respect to microtu-yet the molecular mechanism of duplication remains bule nucleation and organization, of what use are the obscure. This is in stark contrast to chromosomes—the centrioles? One role for the centrioles is to organize the Watson and Crick DNA structure of 1953 was among pericentriolar material into a discrete, stable structure. the greatest " Eureka! " moments in science because it Centrioles can be caused to disassemble by injection revealed in an instant how our genetic material is dupli-into cells of an antibody against a modified form of cated each generation. Chromosomes and centrosomes ␣-tubulin that is found predominantly in centrioles (Bobin-are the only known cell components that are precisely nec et al., 1998). In cells without centrioles, the pericen-duplicated each cell cycle, but the structure of the cen-triolar material disperses, and the centrosome structure trosome does not clearly reveal a mechanism like that is lost. of DNA. It is only in the last few years that substantial Before we can discuss centrosome duplication, we progress has been made in understanding centrosome must understand the origin of the first centrosome in duplication, progress that is continued in a paper pub-development. In most animals, the centrosome and cen-lished in this issue of Cell (O'Connell et al., 2001). In trioles of the oocyte degenerate prior to the meiotic this brief review, I will focus on …