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Encyclopedia > Tumor suppressor gene

A tumor suppressor gene is a gene that reduces the probability that a cell in a multicellular organism will turn into a tumor cell. A mutation or deletion of such a gene will increase the probability of the formation of a tumor. For other uses, see Gene (disambiguation). ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Wild-type Caenorhabditis elegans hermaphrodite stained to highlight the nuclei of all cells Multicellular organisms are organisms consisting of more than one cell, and having differentiated cells that perform specialized functions. ... For malignant tumors specifically, see cancer. ... It has been suggested that mutant be merged into this article or section. ... A genetic deletion is a genetic aberration in which part of a chromosome is missing. ...

Contents

Two-hit hypothesis

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. In other words, tumor suppressors are usually not haploinsufficient, although there are notable exceptions (the p53 gene product). An oncogene is a gene that can cause a cell to develop into a tumor cell, possibly resulting in cancer. ... The Knudson hypothesis is the hypothesis that cancer is the result of accumulated mutations to a cells DNA. It was first proposed by Carl O. Nordling in 1953, [1][2] and later formulated by Alfred G. Knudson in 1971. ... For the hard rock band, see Allele (band). ... Haploinsufficiency occurs when a diploid organism only has a single functional copy of a gene (with the other copy inactivated by mutation) and the single functional copy of the gene does not produce enough of a gene product (typically a protein) to bring about a wild-type condition, leading to... TP53 bound to a short DNA fragment. ...


Functions

Tumor suppressor genes, or more precisely, the proteins for which they code, either have a dampening or repressive effect on the regulation of the cell cycle or promote apoptosis, and sometimes do both. The functions of tumor suppressor proteins fall into several categories including the following:[1] A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication. ... A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (pronounced apo tō sis) is a process of suicide by a cell in a multicellular organism. ...

  1. Repression of genes that 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 DNA in 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 adhesion prevent tumor cells from dispersing, block loss of contact inhibition, and inhibit metastasis.[2]

A repressor is a DNA-binding protein that regulates the expression of one or more genes by decreasing the rate of transcription. ... Protein expression is a subcomponent of gene expression. ... This does not adequately cite its references or sources. ... DNA damage resulting in multiple broken chromosomes DNA repair is a process constantly operating in each cell of a living being; it is essential to survival because it protects the genome from damage. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (pronounced apo tō sis) is a process of suicide by a cell in a multicellular organism. ... Schematic of cell adhesion The study of cell adhesion is part of cell biology. ... The loss of cell division when one cell contact with another cell when optimum size and volume of the tissue has been formed. ... For the musical composition, see Metastasis (Xenakis composition). ...

Examples

The first tumor suppressor protein discovered was the pRb protein in human retinoblastoma; however, recent evidence has also implicated pRb as a tumor survival factor. The Retinoblastoma protein, or pRb, is an important tumor suppressor protein. ... This article is about modern humans. ... // Retinoblastoma is a cancer of the retina. ...


Another important tumor suppressor is the p53 tumor suppressor protein produced by the TP53 gene. TP53 bound to a short DNA fragment. ... TP53 is a tumor suppressor gene that is named after, and provides instructions for making, a protein called tumor protein 53 (TP53). ...


PTEN acts by opposing the action of PI3K, which is essential for anti-apoptotic, pro-tumorogenic Akt activation. PTEN may mean: PTEN gene - one of the tumor suppressor gene (chromosome 10) Prime Time Entertainment Network ... Phosphoinositide 3-kinases (PI 3-kinases or PI3Ks) are a family of related enzymes that are capable of phosphorylating the 3 position hydroxyl group of the inositol ring of phosphatidylinositol (PtdIns)[1]. The various 3-phosphorylated phosphoinositides that are produced by PI 3-kinases (PtdIns3P, PtdIns(3,4)P2, PtdIns... Akt, also known as protein kinase B (PKB) is an important molecule in mammalian cellular signaling. ...


See also

APC (adenomatosis polyposis coli) is a human gene that is classified as a tumor suppressor gene. ... An oncogene is a modified gene that increases the malignancy of a tumor cell. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... DNA damage resulting in multiple broken chromosomes DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. ... In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in what is thought of as... The Von Hippel Lindau Binding protein 1 is a heterohexameric chaperone protein of two PFD-alpha type and four PFD-beta type subunits based on its ability to capture unfolded actin. ...

References

  1. ^ Sherr C (2004). "Principles of tumor suppression". Cell 116 (2): 235-46. PMID 14744434. 
  2. ^ Hirohashi S, Kanai Y (2003). "Cell adhesion system and human cancer morphogenesis". Cancer Sci 94 (7): 575-81. PMID 12841864. 

==External links== *

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

  Results from FactBites:
 
Tumor suppressor gene Summary (1840 words)
By contrast, tumor suppressor genes normally repress, or "put the brakes on," the activation of the pathways.
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.
Tumor suppressor genes, or more precisely, the proteins for which they code, either have a dampening or repressive effect on the regulation of the cell cycle or promote apoptosis, and sometimes do both.
Molecular Guide - MGH Brain Tumor Center (8023 words)
The p53 gene, a tumor suppressor gene located on chromosome 17p, has an integral role in a number of cellular processes, including cell cycle arrest, response to DNA damage, apoptosis, angiogenesis and differentiation; as a result, p53 has been dubbed the "guardian of the genome".
This gene maps to a region of chromosome 19q13.3, telomeric to the marker D19S219 and centromeric to the HRC gene 26,27.
The gene responsible for VHL has been identified 85 and is mutated in sporadic hemangioblastomas 86, suggesting that the VHL gene acts as a classical tumor suppressor and is involved in both sporadic hemangioblastomas and familial tumors.
  More results at FactBites »

 
 

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