Schizosaccharomyces pombe: Difference between revisions
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==Genome structure== | ==Genome structure== | ||
''S. pombe'' was the sixth organism with a nucleus to have its genome sequenced. ''S. pombe'' has a small and compact genome. Its genome contains 13.8 million base pairs distributed among chromosomes I (5.7 Mb), II (4.6 Mb) and III (3.5 Mb) and 4,824 genes. It has the lowest number of protein-coding genes yet identified in a free-living eukaryotic cell ( | ''S. pombe'' was the sixth organism with a nucleus to have its genome sequenced. ''S. pombe'' has a small and compact genome. Its genome contains 13.8 million base pairs distributed among chromosomes I (5.7 Mb), II (4.6 Mb) and III (3.5 Mb) and 4,824 genes. It has the lowest number of protein-coding genes yet identified in a free-living eukaryotic cell (3). The 3 chromosomes are linear, but circular chromosome formation has been observed in fission yeast mutants. If the ''S. pombe'' lose the simple repeats at the very ends of the chromosomes as well as much of the subtelomeric TAS elements, it will fuse end to end to generate circular chromosomes (4). The three centromeres are 35, 65, and 110 kb long for chromosomes I, II, and III respectively. This leaves about 12.5 Mb of unique sequence (3). | ||
A total of 4,730 introns is distributed among 43% of ''S. pombe'' genes, with 15 being the largest number of introns found within a single gene. Of genes that have two or more introns, 614 have two introns, 324 have three, 148 have four, 70 have five and 40 have six (3). Therefore, the number of genes having an extra intron decreases by about half, as intron number increases from two to six per gene (3). These observations may be relevant when we study mechanisms by which introns are generated and removed. The large number of introns in ''S. pombe'' provides opportunities for alternative splicing to generate protein variants, which could have regulatory roles as well as increasing the range of protein types present in the cell (3). | |||
The usefulness of ''S. pombe'' for investigating the functions of genes related to human disease is assessed. Protein-coding genes of ''S. pombe'' were identified that generate products with similarities to proteins coded by 289 genes that are mutated, amplified, or deleted in human disease (3). A total of 172 ''S. pombe'' proteins have similarity with members of this data set of human disease proteins. The largest groups of human disease-related genes are those implicated in cancer. There are 23 such genes and they are involved in DNA damage and repair, checkpoint controls, and the cell cycle, all processes in maintaining genomic stability (3). The cell cycle and checkpoint background of ''S. pombe'' make it a good model organism for studying these particular cancer disease pathways. Other categories represented in S. pombe are those involved in metabolic (12 genes), neurological (13 genes), cardiac (1 gene) and renal (1 gene) disease (3). | |||
==Cell structure and metabolism== | ==Cell structure and metabolism== | ||
Revision as of 21:34, 19 August 2007
A Microbial Biorealm page on the genus Schizosaccharomyces pombe
Classification
Higher order taxa
Superkingdom: Eukaryota, Kingdom: Fungi, Phylum: Ascomycota, Subphylum: Dikarya, Subphylum: Taphrinomycotina, Class: Schizosaccharomycetes, Order: Schizosaccharomycetales, Family: Schizosaccharomycetaceae, Genus: Schizosaccharomyces
Species
Schizosaccharomyces pombe
Also known as: Schizosaccharomyces malidevorans
Description and significance
The fission yeast Schizosaccharomyces pombe is a unicellular eukaryote that is rod shaped. They measure approximately 2 to 3 microns in diameter and 7 to 14 microns in length (1). S. pombe is usually found in sugar-containing fermentations of alcohol from the subtropical regions (2).
Even though its origin dates back to quite a long time ago, it was not widely known before the 1890’s. It was discovered in 1893 when a group working in a Brewery Association Laboratory in Germany was looking at sediment found in millet beer imported from East Africa that gave it an unsavory acidic taste (1). P. Lindner was the first to describe Schizosaccharomyces pombe. He chose as its epithet the Swahili word for beer, pombe (2). It was identified as yeast, and it became known as the fission yeast because it reproduces by means of fission unlike its relative Saccharomyces cerevisiae. The name Schizosaccharomyces was assigned to it because Schizo- means “different,” which had been previously used to describe other fission species.
The sequencing of its genome was significant since S. pombe is a single-celled living archiascomycete fungus that shares many features with cells of more complicated eukaryotes (3). Researchers have identified fifty genes of S. pombe associated with human diseases including cystic fibrosis, hereditary deafness, and diabetes (3). Researchers state that the largest group of human disease-related genes are those implicated in cancer. There are 23 such genes, and they are involved in DNA damage and repair, checkpoint controls, and the cell cycle. All these processes are involved with maintaining genomic stability (3). These discoveries are important because it will allow researchers to find out more about the evolution of one-celled and multi-celled eukaryotic organisms compared to others such as bacteria, which do not have nucleated cells. Further analyses and comparisons should reveal which genes define eukaryotic cells and the transition from one-celled to multi-celled organisms (3).
Genome structure
S. pombe was the sixth organism with a nucleus to have its genome sequenced. S. pombe has a small and compact genome. Its genome contains 13.8 million base pairs distributed among chromosomes I (5.7 Mb), II (4.6 Mb) and III (3.5 Mb) and 4,824 genes. It has the lowest number of protein-coding genes yet identified in a free-living eukaryotic cell (3). The 3 chromosomes are linear, but circular chromosome formation has been observed in fission yeast mutants. If the S. pombe lose the simple repeats at the very ends of the chromosomes as well as much of the subtelomeric TAS elements, it will fuse end to end to generate circular chromosomes (4). The three centromeres are 35, 65, and 110 kb long for chromosomes I, II, and III respectively. This leaves about 12.5 Mb of unique sequence (3).
A total of 4,730 introns is distributed among 43% of S. pombe genes, with 15 being the largest number of introns found within a single gene. Of genes that have two or more introns, 614 have two introns, 324 have three, 148 have four, 70 have five and 40 have six (3). Therefore, the number of genes having an extra intron decreases by about half, as intron number increases from two to six per gene (3). These observations may be relevant when we study mechanisms by which introns are generated and removed. The large number of introns in S. pombe provides opportunities for alternative splicing to generate protein variants, which could have regulatory roles as well as increasing the range of protein types present in the cell (3).
The usefulness of S. pombe for investigating the functions of genes related to human disease is assessed. Protein-coding genes of S. pombe were identified that generate products with similarities to proteins coded by 289 genes that are mutated, amplified, or deleted in human disease (3). A total of 172 S. pombe proteins have similarity with members of this data set of human disease proteins. The largest groups of human disease-related genes are those implicated in cancer. There are 23 such genes and they are involved in DNA damage and repair, checkpoint controls, and the cell cycle, all processes in maintaining genomic stability (3). The cell cycle and checkpoint background of S. pombe make it a good model organism for studying these particular cancer disease pathways. Other categories represented in S. pombe are those involved in metabolic (12 genes), neurological (13 genes), cardiac (1 gene) and renal (1 gene) disease (3).
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Pathology
The yeast Schizosaccaromyces pombe is a harmless, rapidly growing eukaryote. Therefore, there are no pathologies associated with this particular organism.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
Edited by student of Rachel Larsen
