Schizosaccharomyces pombe

Taxobox | name = "Schizosaccharomyces pombe"
regnum = Fungi
phylum = Ascomycota
subphylum = Taphrinomycotina
classis = Schizosaccharomycetes
ordo = Schizosaccharomycetales
familia = Schizosaccharomycetaceae
genus = "Schizosaccharomyces"
species = "S. pombe"
binomial = "Schizosaccharomyces pombe"

"Schizosaccharomyces pombe", also called "fission yeast", is a species of yeast. It is used as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically measure 3 to 4 micrometres in diameter and 7 to 14 micrometres in length. It is also possibly the eukaryote with the shortest genome (about 13.8 million base pairs).

These cells maintain their shape by growing exclusively through the cell tips and divide by medial fission to produce two daughter cells of equal sizes, which makes them a powerful tool in cell cycle research. Such research is critical as it is important to understand how cells grow and differentiate as well as how non-controlled growth results in cancerous cells.

Fission yeast was isolated in 1893 by Lindner from East African millet beer. The species name is derived from the Swahili word for beer (Pombe). It was first developed as an experimental model in the 1950s: by Urs Leupold for studying genetics [Leupold U. (1950) Die Vererbung von Homothallie und Heterothallie bei "Schizosaccharomyces pombe". CR Trav Lab Carlsberg Ser Physiol 24:381-480.] [Leupold U. (1993) The origins of "Schizosaccharomyces pombe" genetics. In: Hall MN, Linder P. eds. The Early Days of Yeast Genetics. New York. Cold Spring Harbor Laboratory Press.. p 125-128.] , and by Murdoch Mitchison for studying the cell cycle [Mitchison JM. (1957) The growth of single cells. I. "Schizosaccharomyces pombe". Exp Cell Res 13:244-262.] [Mitchison JM. (1990) My favourite cell: The fission yeast, "Schizosaccharomyces pombe". Bioessays 4:189-191.] .

The fission yeast researcher Paul Nurse successfully merged the independent schools of fission yeast genetics and cell cycle research. Together with Lee Hartwell and Tim Hunt, Paul Nurse won the 2001 Nobel Prize in Physiology or Medicine, for their work on cell cycle regulation.

The sequence of the "S. pombe" genome was published in 2002, by a consortium led by the Sanger Institute, becoming the sixth model eukaryotic organism whose genome has been fully sequenced. This has fully unlocked the power of this organism, with many genes homologous to human disease genes, including diabetes and cystic fibrosis, being identified.

In 2006, sub-cellular localization of all the proteins in "S. pombe" was published using the green fluorescent protein as a molecular tag.

"S. pombe" has also proved to be an important organism for unlocking the secrets of the cell cycle response to DNA damage and DNA replication.

Comparison with budding yeast or "Saccharomyces cerevisiae"

*"S. cerevisiae" has ~ 5600 open reading frames, "Sch. pombe" has ~ 4800 open reading frames
*"S. cerevisiae" has 16 chromosomes, "Sch. pombe" has 3
*"S. cerevisiae" is usually diploid while "Sch. pombe" is usually haploid
*"S. cerevisiae" is mainly in G1 state (consequently G1-S transition is tightly controlled) while "Sch. pombe" is usually in G2 state (consequently G2-M transition is under tight control)
* Both species share genes with humans that they do not share with each other . "Sch. pombe" contains the same heterochromatin genes as humans; they are missing from "S. cerevisiae". Conversely, "S. cerevisiae" has well developed peroxisomes; "Sch. pombe" does not.
* "S. cerevisiae" has small point centromeres of about 100bp, and sequence-defined replication origins around the same size. Conversely, "Sch. pombe" has large, repetitive centromeres (40-100kb), and degenerate origins of at least 1kb.
*"S. cerevisiae" has no RNAi pathway while "Sch. pombe" does.

External links

* [http://www-rcf.usc.edu/~forsburg/ Pombe Pages]
* [http://www.genedb.org/genedb/pombe/index.jsp Pombe Gene Database]
* [http://www.sanger.ac.uk/Projects/S_pombe/ Pombe Genome at the Sanger Centre]
* [http://www.yeastrc.org/ Yeast Resource Center]
* [http://www.ebi.ac.uk/2can/genomes/eukaryotes/Schizosaccharomyces_pombe.html]
* [http://www3.interscience.wiley.com/cgi-bin/jhome/3895 Wiley's Journal "Yeast"]

References