Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Accumulation of p53 protein was seen in the nuclei of mammalian cells following DNA damage caused by ultraviolet radiation (UV), X-ray, or a restriction enzyme. Promoters containing p53-binding sites show a dramatic transcriptional response to DNA damage. The p53 response to X-ray is rapid, reaching a peak at 2 hr after radiation, but is very transitory and reduced in magnitude compared with that seen in response to UV. We find no substantive defect in the p53 response of cells from ataxia telangiectasia or xeroderma pigmentosum complementation group A patients. In contrast, 2 out of 11 primary cultures from Bloom's patients showed a complete absence of p53 accumulation following UV irradiation or SV40 infection and a grossly delayed and aberrant response following X-ray.
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PMID:Differential induction of transcriptionally active p53 following UV or ionizing radiation: defects in chromosome instability syndromes? 824 48

Cell cycle anomalies have been described in ataxia-telangiectasia cells after exposure to ionizing radiation. A recent report demonstrates that cells from these patients lack the ionizing radiation-induced increase in p53 protein seen in controls. We report here that an ionizing radiation-induced p53 response is reduced and/or delayed in cells from four ataxia-telangiectasia complementation groups. On the other hand, p53 induction is normal in all A-T complementation groups after exposure to UV-B light, an agent to which these cells are not hypersensitive. Specific inhibitors of protein kinase C and serine/threonine phosphatases prevented the radiation induction of p53 protein. Agents that produced double-strand breaks in DNA and/or inhibition of transcription caused an induction of p53 in the absence of radiation in control cells but not in ataxia-telangiectasia, but inhibitors of cell cycle progression such as mimosine and aphidicolin led to an increase in p53 in both cell types in the absence of radiation. These results suggest that there is more than one signal transduction pathway responsible for activation of p53, one of which is less efficient in ataxia-telangiectasia cells.
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PMID:Ionizing radiation and UV induction of p53 protein by different pathways in ataxia-telangiectasia cells. 824 33

Damage to chromosomal DNA increases the levels of the transcriptional regulatory protein p53. We have investigated how the MDM2 protein, which binds to p53 and inactivates its transcriptional activity, may be controlled following DNA damage. Irradiation of human GM2149 fibroblast cells causes an increase in MDM2 mRNA levels within 1 h, and levels remain elevated for at least 8 h. The induction of MDM2 mRNA following irradiation is not blocked by inhibitors of protein synthesis and can be detected after doses of 2-5 Gy. In ataxia telangiectasia cells or cells where p53 is mutated/deleted, MDM2 mRNA levels are not increased after DNA damage. This suggests that p53 is required for transcription of the MDM2 gene following DNA damage.
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PMID:DNA damage increases the levels of MDM2 messenger RNA in wtp53 human cells. 831 78

We describe molecular genetic findings in a patient who initially presented with an intermediate teratoma of the testis and who many years later presented with an oligodendro-astrocytoma. In addition he developed a malignant histiocytoma over the scapula, an adenocarcinoma of the stomach and a late stage adenoma of the sigmoid colon. Due to the development of several neoplasms the possibility of either ataxia telangiectasia or Li-Fraumeni syndrome was considered in differential diagnosis. A molecular genetic investigation revealed that both he and his brother carried a germline p53 tumor suppressor gene mutation at codon 248. From this result we conclude that this family belongs to the Li-Fraumeni syndrome. Once characterized as belonging to the Li-Fraumeni syndrome, the remaining members of the family were typed to determine if they too carried the same mutation. The two children of the index patient were shown not to carry the mutation and are therefore at no increased risk of developing any of the Li-Fraumeni spectrum of malignancies. A molecular genetic investigation into similar families could help to prevent the development of additional malignancies as seen in the index patient, as radiotherapy may interfere with the normal function of the p53 protein and this may in turn help to orchestrate DNA repair after radiation.
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PMID:[Hereditary p53 mutation in a patient with multiple tumors: significance for genetic counseling]. 839 84

Alterations of the TP53 tumor suppressor gene are present in various human malignancies and in the dominantly inherited Li-Fraumeni syndrome. Recently, a cell cycle checkpoint pathway involving p53 and GADD45 has been identified as defective in ataxia-telangiectasia. Using single strand conformation polymorphism analysis of PCR products, we looked for TP53 mutations in DNA of patients with AT. We did not find any mutation in 6 patients, suggesting that TP53 mutations are not directly involved in the cancer susceptibility observed in AT.
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PMID:Lack of mutations in the P53 gene exons 5 to 8 in ataxia-telangiectasia. 850 Jan 1

Ataxia-telangiectasia (A-T) is a human disease characterized by high cancer risk, immune defects, radiation sensitivity, and genetic instability. Although A-T homozygotes are rare, the A-T gene may play a role in sporadic breast cancer and other common cancers. Abnormalities of DNA repair, genetic recombination, chromatin structure, and cell cycle checkpoint control have been proposed as the underlying defect in A-T; however, previous models cannot satisfactorily explain the pleiotropic A-T phenotype. Two recent observations help clarify the molecular pathology of A-T: (a) inappropriate p53-mediated apoptosis is the major cause of death in A-T cells irradiated in culture; and (b) ATM, the putative gene for A-T, has extensive homology to several cell cycle checkpoint genes from other organisms. Building on these new observations, a comprehensive model is presented in which the ATM gene plays a crucial role in a signal transduction network that activates multiple cellular functions in response to DNA damage. In this Damage Surveillance Network model, there is no intrinsic defect in the machinery of DNA repair in A-T homozygotes, but their lack of a functional ATM gene results in an inability to: (a) halt at multiple cell cycle checkpoints in response to DNA damage; (b) activate damage-inducible DNA repair; and (c) prevent the triggering of programmed cell death by spontaneous and induced DNA damage. Absence of damage-sensitive cell cycle checkpoints and damage-induced repair disrupts immune gene rearrangements and leads to genetic instability and cancer. Triggering of apoptosis by otherwise nonlethal DNA damage is primarily responsible for the radiation sensitivity of A-T homozygotes and results in an ongoing loss of cells, leading to cerebellar ataxia and neurological deterioration, as well as thymic atrophy, lymphocytopenia, and a paucity of germ cells. Experimental evidence supporting the Damage Surveillance Network model is summarized, followed by a discussion of how defects in the ATM-dependent signal transduction network might account for the A-T phenotype and what insights this new understanding of A-T can offer regarding DNA damage response networks, genomic instability, and cancer.
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PMID:Ataxia-telangiectasia and cellular responses to DNA damage. 852 80

'Checkpoint' controls arrest the cell cycle after DNA damage, allowing repair to take place before mutations can be perpetuated. In multicellular organisms, DNA damage can also induce apoptotic cell death, protecting the organism at the expense of the individual cell. How does a cell 'choose' between cycle arrest and death? Analysis of two human tumour suppressor proteins, p53 and the ATM (ataxia-telangiectasia mutated) gene product, may provide some answers.
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PMID:Cellular responses to DNA damage: cell-cycle checkpoints, apoptosis and the roles of p53 and ATM. 853 57

A substantial proportion of patients with primary immunodeficiency diseases develop tumors, particularly those of lymphoreticular system caused by Epstein-Barr virus (EBV). Primary immunodeficiency renders patients susceptible to EBV by reducing immune reactions and surveillance abilities against the virus or inducing overreaction of the responding cells to the antigens. Recent progress in molecular biology has unraveled the genes responsible for several types of primary immunodeficiency diseases. The cloning of the ATM gene demonstrated that the mutations in this gene were observed in the members of all the families affected with ataxia telangiectasia (AT), indicating the crucial role of this gene in the pathogenesis of AT. The protein encoded by the ATM gene shows a high sequence homology with several proteins which are presumed to be involved in the regulation of the cell cycle transition. Accumulating evidence indicates that AT-derived cells are sensitive to irradiation due to the abnormalities in p53-dependent cell cycle arrest at G1 phase. Thus, the ATM product may regulate the cell cycle at G1 phase in a p53-dependent manner and the defect of the gene may lead to the accumulation of cells with DNA damages, thereby causing malignant transformation.
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PMID:[Primary immunodeficiency diseases]. 853 51

An estimated 5 to 10% of all breast and ovarian cancer is attributable to inherited mutations in two highly penetrant autosomal dominant susceptibility genes, BRCA1 and BRCA2. BRCA1 confers higher risk of ovarian cancer and BRCA2 much higher risk of male breast cancer. With the exception of missense mutations in the RING finger near the amino terminus of BRCA1, virtually all germline mutations in the gene cause the novel BRCA1 protein to be prematurely truncated. Approximately 90% of breast tumors in BRCA1 families, 50% of unselected breast tumors and 65-80% of unselected ovarian tumors have lost one allele of BRCA1 by somatic deletion. Very few tumors have detectable somatic point mutations in BRCA1. Inhibition of BRCA1 expression in mammary epithelial cell lines also suggests that BRCA1 may act as a tumor suppressor. The biological function of BRCA1 is still unknown, although identification of a patient homozygous for an inherited BRCA1 mutation suggests that the gene's function may be essential only to specific tissues. At least two other genes, P53 and the androgen receptor, are responsible for inherited predisposition to breast cancer in rare families. Several epidemiologic studies suggest that individuals carrying rare alleles at a minisatellite flanking the HRAS locus are at increased risk of cancer, including breast cancer. Finally, preliminary epidemiologic studies also suggest that individuals heterozygous for mutations in the ataxia telangiectasia gene may be at increased risk of breast cancer.
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PMID:Inherited breast and ovarian cancer. 854 81

The molecular basis of radiosensitivity was studied using a cDNA complementation approach to correct radiosensitivity in cells. Four cDNAs of sizes 1.6, 2.0, 2.2 and 2.5 kb were isolated that corrected several aspects of the phenotype of cells from patients with the human genetic disorder ataxia-telangiectasia, characterized by hypersensitivity to ionizing radiation. The criteria used to assess correction included cell viability, induced chromosome aberrations, G2 phase delay and induction of p53 after exposure to radiation. One cDNA (2.5 kb) was identified as the complete sequence of the RNA helicase p68, which was capable of correcting radiosensitivity based on two of the above four criteria, with p53 induction post irradiation being partially corrected. The 2.2 kb cDNA was shown to correspond to the complete sequence of arginyl tRNA synthetase and the other two cDNAs were identical to the 3' untranslated regions (UTR) of the transcription factor TFIIS (1.6 kb) and phospholipase A2 (2.0 kb) respectively. Additional transfections with the 3'UTR (198 nucleotides) of p68 RNA helicase and its inverse sequence revealed that the 3'UTR had the same complementation capacity as the full-length cDNA, whereas the inverse construct failed to complement radiosensitivity. These data provide additional support for a novel role for 3'UTRs in the regulation of gene expression.
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PMID:Genetic complementation of radiation response by 3' untranslated regions (UTR) of RNA. 861 88


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