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)

We describe the events triggered by a sub-lethal concentration of airborne particulate matter (PM(10)) in A549 cells, which include the formation DNA double-strand breaks, gammaH2A.X generation, and 53BP1 recruitment. To protect the genome, cells activated ATM/ATR/Chk1/Chk2/p53 pathway but, after 48 h, cells turned into a senescence-like state. Trolox, an antioxidant, was able to prevent most of the alterations observed after particulate matter exposure, demonstrating the important role of ROS as mediator of PM(10)-induced genotoxicity and suggesting that DNA damage could be the mechanisms by which particulate matter augment the risk of lung cancer.
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PMID:DNA damage response of A549 cells treated with particulate matter (PM10) of urban air pollutants. 1921 10

Contaminated soil is a serious environmental problem, constituting a risk to humans and the environment. Polycyclic aromatic hydrocarbons (PAHs) are often present at contaminated sites. However, risk levels are difficult to estimate because of the complexity of contaminants present. Here, we compare cellular effects of extracts from contaminated soils collected at six industrial settings in Sweden. Chemical analysis showed that all soils contained complex mixtures of PAHs and oxy-PAHs. Western blotting and immunocytochemistry were used to investigate DNA damage signaling in HepG2 cells exposed to extracts from these soils. The effects on phosphorylated Mdm2, p53, Erk, H2AX, 53BP1, and Chk2, cell cycle regulating proteins (cyclin D1 and p21), and cell proliferation were compared. We found that most soil extracts induced phosphorylation of Mdm2 at the 2A10 epitope at low concentrations. This is in line with previous studies suggesting that this endpoint reflects readily repaired DNA-damage. However, we found concentration- and time-dependent gammaH2AX and 53BP1 responses that were sustained for 48 hr. These endpoints may reflect the presence of different types of persistent DNA-damage. High concentrations of soil extracts decreased cyclin D1 and increased p21 response, indicating cell cycle arrest. Phosphorylation of Mdm2 at Ser166, which attenuates the p53 response and is induced by many tumor promoters, was induced in a time-dependent manner and was associated with Erk phosphorylation. Taken together, the PAH extracts elicited unpredictable signaling responses that differed between samples. More polar compounds, i.e., oxy-PAHs, also contributed to the complexity.
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PMID:Exposure of HepG2 cells to low levels of PAH-containing extracts from contaminated soils results in unpredictable genotoxic stress responses. 1930 13

The cellular response to DNA double-strand breaks involves direct activation of ataxia telangiectasia mutated (ATM) and indirect activation of ataxia telangiectasia and Rad3 related (ATR) in an ATM/Mre11/cell-cycle-dependent manner. Here, we report that the crucial checkpoint signalling proteins-p53, structural maintainance of chromosomes 1 (SMC1), p53 binding protein 1 (53BP1), checkpoint kinase (Chk)1 and Chk2-are phosphorylated rapidly by ATR in an ATM/Mre11/cell-cycle-independent manner, albeit at low levels. We observed the sequential recruitment of replication protein A (RPA) and ATR to the sites of DNA damage in ATM-deficient cells, which provides a mechanistic basis for the observed phosphorylations. The recruitment of ATR and consequent phosphorylations do not require Mre11 but are dependent on Exo1. We show that these low levels of phosphorylation are biologically important, as ATM-deficient cells enforce an early G2/M checkpoint that is ATR-dependent. ATR is also essential for the late G2 accumulation that is peculiar to irradiated ATM-deficient cells. Interestingly, phosphorylation of KRAB associated protein 1 (KAP-1), a protein involved in chromatin remodelling, is mediated by DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in a spatio-temporal manner in addition to ATM. We posit that ATM substrates involved in cell-cycle checkpoint signalling can be minimally phosphorylated independently by ATR, while a small subset of proteins involved in chromatin remodelling are phosphorylated by DNA-PKcs in addition to ATM.
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PMID:Distinct roles of ATR and DNA-PKcs in triggering DNA damage responses in ATM-deficient cells. 1944 12

Cellular response to DNA damage involves the coordinated activation of cell cycle checkpoints and DNA repair. The early steps of DNA damage recognition and signaling in mammalian cells are not yet fully understood. To investigate the regulation of the DNA damage response (DDR), we designed short and stabilized double stranded DNA molecules (Dbait) mimicking double-strand breaks. We compared the response induced by these molecules to the response induced by ionizing radiation. We show that stable 32-bp long Dbait, induce pan-nuclear phosphorylation of DDR components such as H2AX, Rpa32, Chk1, Chk2, Nbs1 and p53 in various cell lines. However, individual cell analyses reveal that differences exist in the cellular responses to Dbait compared to irradiation. Responses to Dbait: (i) are dependent only on DNA-PK kinase activity and not on ATM, (ii) result in a phosphorylation signal lasting several days and (iii) are distributed in the treated population in an "all-or-none" pattern, in a Dbait-concentration threshold dependant manner. Moreover, despite extensive phosphorylation of the DNA-PK downstream targets, Dbait treated cells continue to proliferate without showing cell cycle delay or apoptosis. Dbait treatment prior to irradiation impaired foci formation of Nbs1, 53BP1 and Rad51 at DNA damage sites and inhibited non-homologous end joining as well as homologous recombination. Together, our results suggest that the hyperactivation of DNA-PK is insufficient for complete execution of the DDR but induces a "false" DNA damage signaling that disorganizes the DNA repair system.
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PMID:Hyperactivation of DNA-PK by double-strand break mimicking molecules disorganizes DNA damage response. 1962 Oct 83

Cellular nutritional and energy status regulates a wide range of nuclear processes important for cell growth, survival, and metabolic homeostasis. Mammalian target of rapamycin (mTOR) plays a key role in the cellular responses to nutrients. However, the nuclear processes governed by mTOR have not been clearly defined. Using isobaric peptide tagging coupled with linear ion trap mass spectrometry, we performed quantitative proteomics analysis to identify nuclear processes in human cells under control of mTOR. Within 3 h of inhibiting mTOR with rapamycin in HeLa cells, we observed down-regulation of nuclear abundance of many proteins involved in translation and RNA modification. Unexpectedly, mTOR inhibition also down-regulated several proteins functioning in chromosomal integrity and up-regulated those involved in DNA damage responses (DDRs) such as 53BP1. Consistent with these proteomic changes and DDR activation, mTOR inhibition enhanced interaction between 53BP1 and p53 and increased phosphorylation of ataxia telangiectasia mutated (ATM) kinase substrates. ATM substrate phosphorylation was also induced by inhibiting protein synthesis and suppressed by inhibiting proteasomal activity, suggesting that mTOR inhibition reduces steady-state (abundance) levels of proteins that function in cellular pathways of DDR activation. Finally, rapamycin-induced changes led to increased survival after radiation exposure in HeLa cells. These findings reveal a novel functional link between mTOR and DDR pathways in the nucleus potentially operating as a survival mechanism against unfavorable growth conditions.
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PMID:Quantitative nuclear proteomics identifies mTOR regulation of DNA damage response. 1995 88

The ubiquitin-proteasome pathway plays an important role in DNA damage signaling and repair by facilitating the recruitment and activation of DNA repair factors and signaling proteins at sites of damaged chromatin. Proteasome activity is generally not thought to be required for activation of apical signaling kinases including the PI3K-related kinases (PIKKs) ATM, ATR, and DNA-PK that orchestrate downstream signaling cascades in response to diverse genotoxic stimuli. In a previous work, we showed that inhibition of the proteasome by MG-132 suppressed 53BP1 (p53 binding protein1) phosphorylation as well as RPA2 (replication protein A2) phosphorylation in response to the topoisomerase I (TopI) poison camptothecin (CPT). To address the mechanism of proteasome-dependent RPA2 phosphorylation, we investigated the effects of proteasome inhibitors on the upstream PIKKs. MG-132 sharply suppressed CPT-induced DNA-PKcs autophosphorylation, a marker of the activation, whereas the phosphorylation of ATM and ATR substrates was only slightly suppressed by MG-132, suggesting that DNA-PK among the PIKKs is specifically regulated by the proteasome in response to CPT. On the other hand, MG-132 did not suppress DNA-PK activation in response to UV or IR. MG-132 blocked the interaction between DNA-PKcs and Ku heterodimer enhanced by CPT, and hydroxyurea pre-treatment completely abolished CPT-induced DNA-PKcs autophosphorylation, indicating a requirement for ongoing DNA replication. CPT-induced TopI degradation occurred independent of DNA-PK activation, suggesting that DNA-PK activation does not require degradation of trapped TopI complexes. The combined results suggest that CPT-dependent replication fork collapse activates DNA-PK signaling through a proteasome dependent, TopI degradation-independent pathway. The implications of DNA-PK activation in the context of TopI poison-based therapies are discussed.
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PMID:Proteasome inhibition suppresses DNA-dependent protein kinase activation caused by camptothecin. 1995

The p53-inducible gene 3 (PIG3) is originally isolated as a p53 downstream target gene, but its function remains unknown. Here, we report a role of PIG3 in the activation of DNA damage checkpoints, after UV irradiation or radiomimetic drug neocarzinostatin (NCS). We show that depletion of endogenous PIG3 sensitizes cells to DNA damage agents, and impaired DNA repair. PIG3 depletion also allows for UV- and NCS-resistant DNA synthesis and permits cells to progress into mitosis, indicating that PIG3 knockdown can suppress intra-S phase and G2/M checkpoints. PIG3-depleted cells show reduced Chk1 and Chk2 phosphorylation after DNA damage, which may directly contribute to checkpoint bypass. PIG3 exhibited diffuse nuclear staining in the majority of untreated cells and forms discrete nuclear foci in response to DNA damage. PIG3 colocalizes with gamma-H2AX and 53BP1 to sites of DNA damage after DNA damage, and binds to a gamma-H2AX. Notably, PIG3 depletion decreases the efficient induction and maintenance of H2AX phosphorylation after DNA damage. Moreover, PIG3 contributes to the recruitment of 53BP1, Mre11, Rad50 and Nbs1 to the sites of DNA break lesions in response to DNA damage. Our combined results suggest that PIG3 is a critical component of the DNA damage response pathway and has a direct role in the transmission of the DNA damage signal from damaged DNA to the intra-S and G2/M checkpoint machinery in human cells.
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PMID:The p53-inducible gene 3 (PIG3) contributes to early cellular response to DNA damage. 2002 97

In response to DNA double strand breaks, the histone variant H2AX at the break site is phosphorylated at serine 139 by DNA damage sensor kinases such as ataxia telangiectasia-mutated, forming gamma-H2AX. This phosphorylation event is critical for sustained recruitment of other proteins to repair the break. After repair, restoration of the cell to a prestress state is associated with gamma-H2AX dephosphorylation and dissolution of gamma-H2AX-associated damage foci. The phosphatases PP2A and PP4 have previously been shown to dephosphorylate gamma-H2AX. Here, we demonstrate that the wild-type p53-induced phosphatase 1 (WIP1) also dephosphorylates gamma-H2AX at serine 139 in vitro and in vivo. Overexpression of WIP1 reduces formation of gamma-H2AX foci in response to ionizing and ultraviolet radiation and blocks recruitment of MDC1 (mediator of DNA damage checkpoint 1) and 53BP1 (p53 binding protein 1) to DNA damage foci. Finally, these inhibitory effects of WIP1 on gamma-H2AX are accompanied by WIP1 suppression of DNA double strand break repair. Thus, WIP1 has a homeostatic role in reversing the effects of ataxia telangiectasia-mutated phosphorylation of H2AX.
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PMID:Wild-type p53-induced phosphatase 1 dephosphorylates histone variant gamma-H2AX and suppresses DNA double strand break repair. 2011 29

Mice with a complete deficiency of p73 have severe neurological and immunological defects due to the absence of all TAp73 and DeltaNp73 isoforms. As part of our ongoing program to distinguish the biological functions of these isoforms, we generated mice that are selectively deficient for the DeltaNp73 isoform. Mice lacking DeltaNp73 (DeltaNp73(-/-) mice) are viable and fertile but display signs of neurodegeneration. Cells from DeltaNp73(-/-) mice are sensitized to DNA-damaging agents and show an increase in p53-dependent apoptosis. When analyzing the DNA damage response (DDR) in DeltaNp73(-/-) cells, we discovered a completely new role for DeltaNp73 in inhibiting the molecular signal emanating from a DNA break to the DDR pathway. We found that DeltaNp73 localizes directly to the site of DNA damage, can interact with the DNA damage sensor protein 53BP1, and inhibits ATM activation and subsequent p53 phosphorylation. This novel finding may explain why human tumors with high levels of DeltaNp73 expression show enhanced resistance to chemotherapy.
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PMID:Isoform-specific p73 knockout mice reveal a novel role for delta Np73 in the DNA damage response pathway. 2023 13

The tumor suppressor p53 and the DNA repair factor 53BP1 (p53 binding protein 1) regulate gene transcription and responses to genotoxic stresses. Upon DNA damage, p53 undergoes dimethylation at Lys382 (p53K382me2), and this posttranslational modification is recognized by 53BP1. The molecular mechanism of nonhistone methyl-lysine mark recognition remains unknown. Here we report a 1. 6-A-resolution crystal structure of the tandem Tudor domain of human 53BP1 bound to a p53K382me2 peptide. In the complex, dimethylated Lys382 is restrained by a set of hydrophobic and cation-pi interactions in a cage formed by four aromatic residues and an aspartate of 53BP1. The signature HKKme2 motif of p53, which defines specificity, is identified through a combination of NMR resonance perturbations, mutagenesis, measurements of binding affinities and docking simulations, and analysis of the crystal structures of 53BP1 bound to p53 peptides containing other dimethyl-lysine marks, p53K370me2 (p53 dimethylated at Lys370) and p53K372me2 (p53 dimethylated at Lys372). Binding of the 53BP1 Tudor domain to p53K382me2 may facilitate p53 accumulation at DNA damage sites and promote DNA repair as suggested by chromatin immunoprecipitation and DNA repair assays. Together, our data detail the molecular mechanism of p53-53BP1 association and provide the basis for deciphering the role of this interaction in the regulation of p53 and 53BP1 functions.
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PMID:Structural insight into p53 recognition by the 53BP1 tandem Tudor domain. 2030 47


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