ATM signaling and 53BP1

The Wistar Institute, USA.
Radiotherapy and Oncology (Impact Factor: 4.36). 09/2005; 76(2):119-22. DOI: 10.1016/j.radonc.2005.06.026
Source: PubMed

ABSTRACT The ATM (mutated in Ataxia-Telangiectasia) protein kinase is an important player in signaling the presence of DNA double strand breaks (DSBs) in higher eukaryotes. Recent studies suggest that ATM monitors the presence of DNA DSBs indirectly, through DNA DSB-induced changes in chromatin structure. One of the proteins that sense these chromatin structure changes is 53BP1, a DNA damage checkpoint protein conserved in all eukaryotes and the putative ortholog of the S. cerevisiae RAD9 protein. We review here the mechanisms by which ATM is activated in response to DNA DSBs, as well as key ATM substrates that control cell cycle progression, apoptosis and DNA repair.

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    • "BRCA1 is required for DNA damage-induced S and G2/M phase arrest (Stecklein et al. 2012; Zhu and Dutta 2006), supporting that AFG1-induced S phase arrest of B-2A13 cells and subsequently mediated DNA damages. ATM and ATR can also directly phosphorylate p53 at Ser15 after DSBs occurred, thereby increasing its transactivation activity (Serrano et al. 2013; Zgheib et al. 2005). p53 transcriptionally regulates many pro-apoptotic genes, such as Bax and Puma (Shen and White 2001). "
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    ABSTRACT: Cytochrome P450 2A13 (CYP2A13) is an extrahepatic enzyme that mainly expresses in human respiratory system, and it is reported to mediate the metabolic activation of aflatoxin B1. Due to the structural similarity, AFG1 is predicted to be metabolized by CYP2A13. However, the role of CYP2A13 in metabolic activation of AFG1 is unclear. In present study, human bronchial epithelial cells that stably express CYP2A13 (B-2A13) were used to conduct the effects of AFG1 on cytotoxicity, apoptosis, DNA damages, and their response protein expression. Low concentrations of AFG1 induced significant cytotoxicity and apoptosis, which was consistent with the increased expressions of pro-apoptotic proteins, such as C-PARP and C-caspase-3. In addition, AFG1 increased 8-OHdG and γH2AX in the nuclies and induced S phase arrest and DNA damage in B-2A13 cells, and the proteins related to DNA damage responses, such as ATM, ATR, Chk2, p53, BRCA1, and γH2AX, were activated. All the above effects were inhibited by nicotine (a substrate of CYP2A13) or 8-MOP (an inhibitor of CYP enzymes), confirming that CYP2A13 mediated the AFG1-induced cytotoxicity and DNA damages. Collectively, our findings first demonstrate that CYP2A13 might be an efficient enzyme in metabolic activation of AFG1 and helps provide a new insight into adverse effects of AFG1 in human respiratory system.
    Archives of Toxicology 08/2013; 87(9). DOI:10.1007/s00204-013-1108-3 · 5.98 Impact Factor
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    • "In the present study, EP inhibited the increase in oxidative DNA damage induced by MGO. When DNA is damaged, cells initiate a cell cycle delay or induction of apoptosis [39]. Diabetes-induced oxidative stress has been well documented in patients and animals [40] [41] [42]. "
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    ABSTRACT: Pyruvate is an endogenous antioxidant substance. The aim of this study was to investigate the protective effects of ethyl pyruvate (EP) on retinal vascular injury in diabetic retinopathy. To investigate the protective effect of EP on vascular cell apoptosis and blood-retinal barrier (BRB) breakage, we have used intravitreally methylglyoxal-(MGO-) injected rat eyes. Apoptosis of the retinal vascular cell that was stimulated by the intravitreal injection of MGO was evidently attenuated by the EP treatment. EP exerts inhibitory effect on MGO-induced vascular cell apoptosis by blocking oxidative injury. In addition, EP treatment prevented MGO-induced BRB breakage and the degradation of occludin, an important tight junction protein. These observations suggest that EP acts through an antioxidant mechanism to protect against oxidative stress-induced apoptosis in retinal vessels.
    Journal of Diabetes Research 02/2013; 2013:460820. DOI:10.1155/2013/460820 · 2.16 Impact Factor
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    • "Oxidation of guanine to form 8-OHdG acts as a marker of oxidative DNA damage [24]. When DNA is damaged, cells initiate a response, such as DNA repair, cell-cycle delay, or induction of apoptosis [25]. Increased levels of 8-OHdG have been reported in urine [26], mononuclear cells [27] and skeletal muscles [28] of diabetic patients. "
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    ABSTRACT: Hyperglycemia promotes oxidative stress and hence generation of reactive oxygen species (ROS), which is known to play a crucial role in the pathogenesis of diabetic nephropathy. Metformin, an oral hypoglycemic drug, possesses antioxidant effects. The aim of this paper is to investigate the protective effects of metformin on the injury of renal podocytes in spontaneously diabetic Torii (SDT) rats, a new model for nonobese type 2 diabetes. Metformin (350 mg/kg/day) was given to SDT rats for 17 weeks. Blood glucose, glycated haemoglobin (HbA1c), and albuminuria were examined. Kidney histopathology, renal 8-hydroxydeoxyguanosine (8-OHdG) levels and apoptosis were examined. In 43-week-old SDT rats, severe hyperglycemia was developed, and albuminuria was markedly increased. Diabetes induced significant alterations in renal glomerular structure. In addition, urinary and renal 8-OHdG levels were highly increased, and podocyte loss was shown through application of the TUNEL and synaptopodin staining. However, treatment of SDT rats with metformin restored all these renal changes. Our data suggested that diabetes-induced podocyte loss in diabetic nephropathy could be suppressed by the antidiabetes drug, metformin, through the repression of oxidative injury.
    Experimental Diabetes Research 09/2012; 2012:210821. DOI:10.1155/2012/210821 · 4.33 Impact Factor
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