Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

The human genetic disorder ataxia-telangiectasia (AT) is characterized by immunodeficiency, progressive cerebellar ataxia, radiosensitivity, cell cycle checkpoint defects and cancer predisposition. The gene mutated in this syndrome, ATM (for AT mutated), encodes a protein containing a phosphatidyl-inositol 3-kinase (PI-3 kinase)-like domain. ATM also contains a proline-rich region and a leucine zipper, both of which implicate this protein in signal transduction. The proline-rich region has been shown to bind to the SH3 domain of c-Abl, which facilitates its phosphorylation and activation by ATM. Previous results have demonstrated that AT cells are defective in the G1/S checkpoint activated after radiation damage and that this defect is attributable to a defective p53 signal transduction pathway. We report here direct interaction between ATM and p53 involving two regions in ATM, one at the amino terminus and the other at the carboxy terminus, corresponding to the PI-3 kinase domain. Recombinant ATM protein phosphorylates p53 on serine 15 near the N terminus. Furthermore, ectopic expression of ATM in AT cells restores normal ionizing radiation (IR)-induced phosphorylation of p53, whereas expression of ATM antisense RNA in control cells abrogates the rapid IR-induced phosphorylation of p53 on serine 15. These results demonstrate that ATM can bind p53 directly and is responsible for its serine 15 phosphorylation, thereby contributing to the activation and stabilization of p53 during the IR-induced DNA damage response.
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PMID:ATM associates with and phosphorylates p53: mapping the region of interaction. 984 17

Ataxia-telangiectasia (AT) syndrome (cerebellar ataxia, oculocutaneous telangiectasias, immunodeficiency, susceptibility to infections, and neoplasia) is associated with cyto- and nucleomegaly in several organ systems. Our aim was to determine (1) whether such cellular abnormalities in the pituitary selectively involve specific cell types, and (2) the proliferation and DNA ploidy status of such cells. Three AT autopsy pituitaries were studied by histology, immunohistochemistry (pituitary hormones, MIB-1, p53 protein), in situ hybridization (pituitary hormones), and Feulgen stain image analysis for ploidy. Results indicated that, in adenohypophyses the scattered pleomorphic, bizarre nuclei were mainly those of somatotrophs and corticotrophs, growth hormone (GH), or adrenocorticotropic hormone (ACm) immunoreactive and expressing the GH or ACTH gene, respectively. Cyto- and nucleomegaly were less frequent in other secretory cells but were also noted in pituicytes of the posterior lobe. Affected cells were immunonegative for MIB-1 and for p53 protein. Image morphometric DNA analysis showed the bizarre cells to be aneuploid with complex histogram patterns, including many nuclei with DNA contents >8 n. No adenomas were found. We conclude that in AT adenohypophyseal cells with cyto- and nucleomegaly, as well as pleomorphism, synthesize and store adenohypophyseal hormones, mainly GH or ACTH. They and affected pituicytes are nonproliferative and are aneuploid.
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PMID:Pituitary Changes in Ataxia-Telangiectasia Syndrome: An Immunocytochemical, In Situ Hybridization, and DNA Cytometric Study of Three Cases. 1211 23

The authors report four adult-onset ataxia telangiectasia (AT) patients belonging to two families lacking pronounced cerebellar ataxia but displaying distal spinal muscular atrophy. AT was proven by genetic studies showing ATM mutations and a reduced level of ATM. ATM activity, as measured by phosphorylation of p53, was close to normal, indicating that the p53 response is not the only factor in preventing neural damage in anterior horn cells in AT.
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PMID:Distal spinal muscular atrophy as a major feature in adult-onset ataxia telangiectasia. 1686 38

The locus for autosomal recessive infantile cerebellar ataxia (CLA3 or SCAR6) has been mapped to chromosome 20q11-q13 in a single Norwegian pedigree. We identified a relatively uncharacterised mouse gene Tp53inp2, and showed that its human orthologue mapped within this candidate interval. Tp53inp2 appears to encode a mammalian-specific protein with homology to the two Tp53inp1 isoforms that respond to cellular stress and interact with p53. We show that Tp53inp2 expression is highly restricted during mouse embryogenesis, with strong expression in the developing brain and spinal cord, as well as in the sensory and motor neuron tracts of the peripheral nervous system. Given this expression pattern, the neurological phenotype of CLA3 and the chromosomal localisation of TP53INP2, we searched the coding region for mutations in samples from individuals from the CLA3 pedigree. Our failure to detect causative mutations suggests that alterations in the coding region of TP53INP2 are not responsible for ataxia in this family, although we cannot rule out changes in non-coding elements of this gene.
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PMID:The coding region of TP53INP2, a gene expressed in the developing nervous system, is not altered in a family with autosomal recessive non-progressive infantile ataxia on chromosome 20q11-q13. 1723 54

Ribosomal stress is an important, yet poorly understood, mechanism that results in activation of the p53 tumour suppressor. We present a mutation in the ribosomal protein Rpl27a gene (sooty foot ataxia mice), isolated through a sensitized N-ethyl-N-nitrosourea (ENU) mutagenesis screen for p53 pathway defects, that shares striking phenotypic similarities with high p53 mouse models, including cerebellar ataxia, pancytopenia and epidermal hyperpigmentation. This phenocopy is rescued in a haploinsufficient p53 background. A detailed examination of the bone marrow in these mice identified reduced numbers of haematopoietic stem cells and a p53-dependent c-Kit down-regulation. These studies suggest that reduced Rpl27a increases p53 activity in vivo, further evident with a delay in tumorigenesis in mutant mice. Taken together, these data demonstrate that Rpl27a plays a crucial role in multiple tissues and that disruption of this ribosomal protein affects both development and transformation.
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PMID:Rpl27a mutation in the sooty foot ataxia mouse phenocopies high p53 mouse models. 2167 2

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder characterized by cerebellar ataxia and oculocutaneous telangiectasias. The gene mutated in this disease, ATM (A-T, mutated), encodes a 370-kDa Ser/Thr protein kinase. ATM not only mediates cellular response to DNA damage but also acts as an activator of Akt in response to insulin. However, despite intensive studies, the mechanism underlying the neuronal degeneration symptoms of human A-T is still poorly understood. We found that the topoisomerase inhibitors etoposide and camptothecin readily induced apoptosis in undifferentiated proliferating SH-SY5Y cells but could not induce apoptosis in neuronally differentiated SH-SY5Y cells. In addition, etoposide induced p53 phosphorylation and H2AX foci formation in proliferating SH-SY5Y cells but failed to do so in differentiated SH-SY5Y cells. Moreover, while inhibition of ATM in undifferentiated SH-SY5Y cells partially protected them from etoposide-induced apoptosis, the same treatment had no effect on cell viability in differentiated SH-SY5Y cells. These results suggest that DNA damage or defective response to DNA damage is not the cause of neuronal cell death in human A-T. In contrast, we discovered that Akt phosphorylation was inhibited when ATM activity was suppressed in differentiated SH-SY5Y cells. Furthermore, inhibition of ATM induced apoptosis following serum starvation in neuronally differentiated SH-SY5Y cells but could not trigger apoptosis under the same conditions in undifferentiated proliferating SH-SY5Y cells. These results demonstrate that ATM mediates the Akt signaling and promotes cell survival in neuron-like human SH-SY5Y cells, suggesting that impaired activation of Akt is the reason for neuronal degeneration in human A-T.
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PMID:Functional switching of ATM: sensor of DNA damage in proliferating cells and mediator of Akt survival signal in post-mitotic human neuron-like cells. 2273 65

The Purkinje cell (PC) degeneration (pcd) mouse harbors a mutation in Agtpbp1 gene that encodes for the cytosolic carboxypeptidase, CCP1. The mutation causes degeneration and death of PCs during the postnatal life, resulting in clinical and pathological manifestation of cerebellar ataxia. Monogenic biallelic damaging variants in the Agtpbp1 gene cause infantile-onset neurodegeneration and cerebellar atrophy, linking loss of functional CCP1 with human neurodegeneration. Although CCP1 plays a key role in the regulation of tubulin stabilization, its loss of function in PCs leads to a severe nuclear phenotype with heterochromatinization and accumulation of DNA damage. Therefore, the pcd mice provides a useful neuronal model to investigate nuclear mechanisms involved in neurodegeneration, particularly the nucleolar stress. In this study, we demonstrated that the Agtpbp1 gene mutation induces a p53-dependent nucleolar stress response in PCs, which is characterized by nucleolar fragmentation, nucleoplasmic and cytoplasmic mislocalization of nucleolin, and dysfunction of both pre-rRNA processing and mRNA translation. RT-qPCR analysis revealed reduction of mature 18S rRNA, with a parallel increase of its intermediate 18S-5'-ETS precursor, that correlates with a reduced expression of Fbl mRNA, which encodes an essential factor for rRNA processing. Moreover, nucleolar alterations were accompanied by a reduction of PTEN mRNA and protein levels, which appears to be related to the chromosome instability and accumulation of DNA damage in degenerating PCs. Our results highlight the essential contribution of nucleolar stress to PC degeneration and also underscore the nucleoplasmic mislocalization of nucleolin as a potential indicator of neurodegenerative processes.
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PMID:Nucleolin reorganization and nucleolar stress in Purkinje cells of mutant PCD mice. 3090 67