Schizosaccharomyces pombe, or fission yeast, is an
African brewing yeast originally isolated from millet beer. This
species has a distinguished research history in studies of the
cell cycle and mitosis, chromosome dynamics, and epigenetics. More
recently, it has been used to address other cell biological
questions including, but not limited to, DNA repair, meiosis,
cytokinesis and mRNA processing. Fission yeast forms
a rod-shaped cell that grows by elongation and divides by medial
fission. With a doubling time of 2-4 hours and simple culture
conditions, S. pombe is easily adapted to any molecular
biology laboratory. Investigators from non-genetic systems
are frequent recruits to the fission yeast community, using S.
pombe as a genetic adjunct in their laboratories, which
has led to S. pombe being nicknamed the “micro-mammal”.
The genome is sequenced with approximately 4979 genes in about 14 Mb of total
DNA, making it the smallest free-living eukaryote. There are only
three chromosomes in the haploid. Importantly, fission yeast does not
share synteny with budding yeast. In fact, the Schizosasccharomyces genus
is frequently classified as an archaeascomycete and is highly diverged from
the familiar ascomycete lineage that includes Saccharomyces or Neurospora. The
fission yeast genome does not have many duplicated genes, making functional
genetics more approachable. Significantly, several groups
of genes are conserved in S. pombe and humans, but missing in S.
cerevisiae, including genes involved in heterochromatin and telomere function,
some splicing genes, and components of the RNAi machinery. Thus,
fission yeast provides a model for study of these functions that is not available
in other systems. The planned sequencing of related species will facilitate
comparative genomics approaches.
Fission yeast is genetically very tractable, and can
be maintained in the haploid or the diploid state. Classical
genetic methods including mutagenesis, selection, suppressor
and synthetic lethal analysis, tetrad dissection and random
spore analysis are all readily performed in this system. S.
pombe can be rapidly transformed with a wide selection
of pombe-specific integrating or episomal plasmids. Gene
disruption (knock-outs) and integration (knock-ins) are straightforward. The
cells are very regular in size and shape, with well-distinguished
nuclei, which facilitates cytological analysis. Biochemistry
is increasingly popular, and proteomics approaches using tandem-affinity
purification and mass spectrometry are now common. Commercial
genomics tools are also available.
Fission yeast is a popular system worldwide and the
community, while dispersed, is vibrant and interactive. A
number of fission-yeast specific meetings are held, and much
communication occurs electronically through web sites and
an e-mailing list.
Susan L. Forsburg, PhD, University
of Southern California