Trisha N. Davis
First recognized over one hundred years ago as a key organizer of cellular structure, the centrosome remains one of the great mysteries of modern cell biology. From the molecular composition, to the structural organization, to the intriguing process of duplication, our understanding is rudimentary. Cells start the cell cycle with a single centrosome which duplicates only once each cycle. The two centrosomes organize the microtubules that make up the mitotic spindle and thereby play a crucial role in ensuring that each daughter cell receives exactly one copy of each chromosome. In cancer cells, this process goes awry resulting in cells with multiple centrosomes as well as abnormal mitotic spindles.
The functional equivalent of the centrosome in the unicellular eukaryote Saccharomyces cerevisiae is a cylindrical multilayered structure called the spindle pole body (SPB). As the name suggests, the two SPBs form the poles of the mitotic spindle. They also organize the cytoplasmic microtubules that reach to the cortex of the cell and position the nucleus. Although SPBs do not resemble centrosomes on the ultrastructural level, the majority of known SPB components have homologues found in the animal cell centrosome. The centrosome and the SPB perform similar functions and contain similar components. Thus, a detailed understanding of the regulation, structure and assembly of the yeast SPB will yield important insights into animal cell centrosomes. We are exploiting our ability to manipulate yeast genes at will to define the properties of this central and essential organizer.