ATM (Ataxia-Telangiectasia Mutated gene) codes for serine-protein kinase ATM protein, which belongs to the PI3/PI4-kinase family proteins. These protein are activated by DNA damage and regulate several other key proteins involved in cell cycle checkpoints, DNA repair, or apoptosis, such as tumor suppressor proteins p53 and BRCA1, checkpoint kinase CHK2, checkpoint proteins RAD17 and RAD9, and DNA repair protein NBS1. ATM protein also plays an important role in the normal development and activity of several body systems, including the nervous system and the immune system.
Mutations in the ATM gene have been identified in patients with ataxia-telangiectasia (A-T). ATM mutations can lead to premature cell death, particularly in the cerebellum, which is involved in coordinating movements. This defect causes the movement problems characteristic of ataxia-telangiectasia. In addition, the deficiency of ATM protein prevents efficient repair of DNA damage, leading to the accumulation of mutations in other genes. This build-up of mutations probably allows cancerous tumors to develop. It was found that the carrier of ATM mutations which cause A-T are more likely than people without an ATM mutation to develop cancer, particularly breast cancer. For example, female A-T patients have a two-fold higher chance of having breast cancer. Also, it was suggested that the carriers of a mutation in the ATM gene may have an increased risk of heart disease.