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.
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