Medical Definition of ATM
ATM: Symbol for the ataxia telangiectasia mutated (ATM) gene. The protein made by the ATM gene functions to control the rate at which cells grow. The ATM protein does this by sending signals and modifying proteins in the cell, which then alters the function of the proteins. This protein also interacts with other proteins (for example BRCA1) to respond when DNA is damaged as a result of exposure to some type of radiation. If the strands of DNA are broken, the ATM protein coordinates DNA repair by activating other proteins. This function helps to maintain the stability of the cell's genome. Because of its central role in cell division and DNA repair, the ATM protein is important to cancer biology.
Mutations in the ATM gene cause ataxia-telangiectasia, an autosomal recessive disorder. (People with this disorder have two mutated copies of ATM.) The mutated ATM gene makes a protein that does not function properly because it is truncated (abnormally short). As a result, the cells are hypersensitive to radiation and do not respond correctly to DNA damage. Instead of activating DNA repair, the defective ATM protein allows mutations to accumulate in other genes. In addition, ATM mutations may allow cells to die inappropriately, particularly in the cerebellum (the part of the brain involved in coordinating movements).
People who have mutations in one copy of the ATM gene, particularly those who have at least one family member with ataxia-telangiectasia, may be at an increased risk of developing breast cancer.
The ATM gene is located in chromosome band 11q22.3. The protein encoded by this gene belongs to the PI3/PI4-kinase family. This protein is a cell cycle checkpoint kinase that phosphorylates and functions as a regulator of a wide variety of downstream proteins, including tumor suppressor proteins p53 and BRCA1, checkpoint kinase CHK2, checkpoint proteins RAD17 and RAD9, and DNA repair protein NBS1. The ATM protein and the closely related kinase ATR are thought to be master controllers of cell cycle checkpoint signaling pathways that are required for cell response to DNA damage and for genome stability.
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