In the February 21 Nature, an international consortium of laboratories, led by the British Nobel laureate Paul Nurse, reports the complete sequence of the fission yeast Schizosaccharomyces pombe (Nature 2002 415:871-880). The depth of sequence coverage was about eight-fold. The three chromosomes make up a 13.8 Mb genome, which is similar in size to that of the budding yeast S. cerevisiae, but considerably smaller than the other sequenced eukaryotic genomes (fruitfly, nematode worm, human and Arabidopsis). The authors predict a maximum of 4,940 protein coding genes, which is about six hundred less than S. cerevisiae and considerably less than the largest prokaryote genomes, emphasising that the differences between prokaryotic and eukaryotic functions does not reside simply in the total number of genes. The S. pombe genome is also less compact than that of S. cerevisiae, with one gene every 2.5 kb and longer intergenic regions. The S. pombe centromeres are 300-1000 times larger than those of its yeast cousin. There are also many more introns (4,730 in 43% of genes) than in S. cerevisiae (5% of genes); this suggests greater opportunity for alternative splicing and protein variants with different regulatory roles. The authors have carried out extensive comparison with other sequenced genomes. The S. pombe proteome has homologs in common with both S. cerevisiae and C. elegans (67%), with S. cerevisiae alone (16%), with C. elegans alone (3%), as well as apparently unique proteins (14%). They found around fifty S. pombe proteins that resemble human proteins implicated in disease; these include several cancer-related proteins linked to DNA damage repair, the cell cycle and genome stability. Comparison with prokaryote genomes indicates the minimal sets of proteins that are specifically important for eukaryotic cell organization and functions. These include those involved in chromatin organisation, nuclear transport, the cytoskeleton and protein stability or modification. Comparison of all the eukaryote and prokaryote genomes available allowed the authors to speculate that "the evolutionary transition from unicellular prokaryotic to unicellular eukaryotic life may have been more complex than the transition to multicellular life."
Readers interested in the comparative genomics and evolutionary history of Schizosaccharomyces pombe might like to read the following articles previously published in Genome Biology:
Minireview: Where does fission yeast sit on the tree of life? Matthias Sipiczki. Genome Biology 2000, 1(2):reviews1011.1-1011.4http://genomebiology.com/2000/1/2/reviews/1011
Minireview: Membrane traffic between genomesJohn Armstrong. Genome Biology 2000, 1(1):reviews104.1-104.4http://genomebiology.com/2000/1/1/reviews/104
Schizosaccharomyces pombe GeneMaps
Proteome database registration
Minireview: Where does fission yeast sit on the tree of life? Matthias Sipiczki. Genome Biology 2000, 1(2):reviews1011.1-1011.4
Minireview: Membrane traffic between genomesJohn Armstrong. Genome Biology 2000, 1(1):reviews104.1-104.4