Tumor suppressor gene

A tumor suppressor gene is a genethat reduces the probability that a cellin a multicellular organismwill turn into a tumorcell. A mutationor deletionof such a gene will increase the probability of the formation of a tumor.

Unlike oncogenes, tumor suppressor genes generally follow the 'two-hit hypothesis,' which implies that both alleles that code for a particular gene must be affected before an effect is manifested. This is due to the fact that if only one allele for the gene is damaged, the second can still produce the correct protein. However, there are cases where mutations in only one allele will cause an effect. A notable example is the gene that codes for p53.

Tumor suppressor genes, or more precisely, the proteinsfor which they code, either have a dampening or repressive effect on the regulation of the cell cycleor promote apoptosis, and sometimes do both. The functions of tumor suppressor proteins fall into several categories [1]including:

1. Repression of genesthat are essential for the continuing of the cell cycle. If these genes are not expressed, the cell cycle will not continue, effectively inhibiting cell division.
2. Coupling the cell cycle to DNA damage. As long as there is damaged DNAin the cell, it should not divide. If the damage can be repaired, the cell cycle can continue.
3. If the damage can not be repaired, the cell should initiate apoptosis, or programmed cell death, to remove the threat it poses for the greater good of the organism.
4. Some proteins involved in cell adhesionprevent tumor cells from dispersing, block loss of contact inhibition, and inhibit metastasis[2]

The first tumor suppressor protein discovered was the pRb protein in humanretinoblastoma; however, recent evidence has also implicated pRb as a tumor survival factor. Another important tumor suppressor is the p53 gene.

See also

• Cancer
• Signal transduction
• DNA repair
• adenomatosis polyposis coli

External links

• Cancer Medicine, online textbook.
• Human Molecular Genetics, online textbook.
• Introduction to Genetic Analysis, online textbook.
• TCF21 gene discovery at Ohio State University

fi:Kasvurajoitegeeni de:Tumorsuppressorgen

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Tumor+suppressor+gene Wikipedia article Tumor suppressor gene.