• Journal of Genetic Medicine
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• v.15 no.2
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• pp.110-114
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• 2018

Ataxia-telangiectasia (AT; OMIM 208900) is a rare autosomal recessive inherited progressive neurodegenerative disorder, with onset in early childhood. AT is caused by homozygous or compound heterozygous mutations in ATM (OMIM 607585) on chromosome 11q22. The average prevalence of the disease is estimated at 1 of 100,000 children worldwide. The prevalence of AT in the Republic of Korea is suggested to be extremely low, with only a few cases genetically confirmed thus far. Herein, we report a 5-year-old Korean boy with clinical features such as progressive gait and truncal ataxia, both ankle spasticity, dysarthria, and mild intellectual disability. The patient was identified as a compound heterozygote with two novel genetic variants: a paternally derived c.5288_5289insGA p.(Tyr1763*) nonsense variant and a maternally derived c.8363A>C p.(His2788Pro) missense variant, as revealed by next-generation sequencing and confirmed by Sanger sequencing. Based on claims data from the Health Insurance Review and Assessment Service Republic of Korea, we calculated the prevalence of AT in the Republic of Korea to be about 0.9 per million individuals, which is similar to the worldwide average. Therefore, we suggest that multi-gene panel sequencing including ATM should be considered early diagnosis.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.16
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• pp.6485-6488
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• 2014

Research over the years has progressively and sequentially provided near complete resolution of regulators of the DNA repair pathways which are so important for cancer prevention. Ataxia-telangiectasia mutated kinase (ATM), a high-molecular-weight PI3K-family kinase has emerged as a master regulator of DNA damage signaling and extensive cross-talk between ATM and downstream proteins forms an interlaced signaling network. There is rapidly growing scientific evidence emphasizing newly emerging paradigms in ATM biology. In this review, we provide latest information regarding how oxidative stress induced activation of ATM can be utilized as a therapeutic target in different cancer cell lines and in xenografted mice. Moreover, crosstalk between autophagy and ATM is also discussed with focus on how autophagy inhibition induces apoptosis in cancer cells.

• Environmental Mutagens and Carcinogens
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• v.22 no.1
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• pp.54-59
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• 2002

We have used cDNA microarray hybridization to identify gene regulated in response to gamma-irradiation in U-937 cell. The cDNA-chip was composed entirely of 1,000 human cancer related gene including apoptosis and angiogenesis etc. In gamma-irradiated U-937 cell, highly charged protein, ribosomal protein L32, four and a half LIM domains 3, lipocalin 2 (oncogene 24p3) and interleukin 15, ataxia telangiectasia mutated (includes complementation groups A, C and D) genes showed increased level of its transcription, and cell division cycle 25A, dihydrofolate reductase, topoisomerase (DNA) II beta(180kD), kinase suppressor of ras and strarigin genes showed reduced level of its transcription compared to untreated U-937 cell. The significant change of level of transcription was not found in well-known ionizing radiation(IR)-responsive gene, such as transcription factor TP53 and p53 related gene, except ataxia telangiectasia mutated gene.

• Biomolecules & Therapeutics
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• v.31 no.5
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• pp.559-565
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• 2023

Ataxia-telangiectasia mutated (ATM), a master kinase of the DNA damage response (DDR), phosphorylates a multitude of substrates to activate signaling pathways after DNA double-strand breaks (DSBs). ATM inhibitors have been evaluated as anticancer drugs to potentiate the cytotoxicity of DNA damage-based cancer therapy. ATM is also involved in autophagy, a conserved cellular process that maintains homeostasis by degrading unnecessary proteins and dysfunctional organelles. In this study, we report that ATM inhibitors (KU-55933 and KU-60019) provoked accumulation of autophagosomes and p62 and restrained autolysosome formation. Under autophagy-inducing conditions, the ATM inhibitors caused excessive autophagosome accumulation and cell death. This new function of ATM in autophagy was also observed in numerous cell lines. Repression of ATM expression using an siRNA inhibited autophagic flux at the autolysosome formation step and induced cell death under autophagy-inducing conditions. Taken together, our results suggest that ATM is involved in autolysosome formation and that the use of ATM inhibitors in cancer therapy may be expanded.

• Archives of Pharmacal Research
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• v.21 no.6
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• pp.640-644
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• 1998

AT cells exhibit defective cell cycle regulation following DNA damage. Previous studies have shown that induction of p53 and p2i proteins are delayed in response to ionizing rad iation, resulting in the failure of G1/S checkpoint in AT cells. In this study, further investigation of the molecular mechanisms underlying G1/S phase progression in AT cells was conducted. Exponentially growing normal and AT cells were exposed to 2 Gly of ionizing radiation and the expression levels and functional activities of Rb and E2F-1 proteins were determined. We observed overexpression of hyperphosphorylated Rb and E2F-1 proteins in AT cells, which was unaffected post-irradiation. Furthermore, gel shift assays showed that E2F-1-DNA binding was constitutive in AT cells, whereas it was inhibited in control cells following exposure to ionizing radiation. The data suggests that abnormalities in the function of Rb and E2F-1 proteins may also be responsible for the failure of AT cells to arrest in the G1/S checkpoint in response to DNA damage.

• BMB Reports
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• v.44 no.5
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• pp.352-357
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• 2011

The effect of human MutY homolog (hMYH) on the activation of checkpoint proteins in response to hydroxyurea (HU) and ultraviolet (UV) treatment was investigated in hMYH-disrupted HEK293 cells. hMYH-disrupted cells decreased the phosphorylation of Chk1 upon HU or UV treatment and increased the phosphorylation of Cdk2 and the amount of Cdc25A, but not Cdc25C. In siMYH-transfected cells, the increased rate of phosphorylated Chk1 upon HU or UV treatment was lower than that in siGFP-transfected cells, meaning that hMYH was involved in the activation mechanism of Chk1 upon DNA damage. The phosphorylation of ataxia telangiectasia and Rad3-related protein (ATR) upon HU or UV treatment was decreased in hMYH-disrupted HEK293 and HaCaT cells. Co-immunoprecipitation experiments showed that hMYH was immunoprecipitated by anti-ATR. These results suggest that hMYH may interact with ATR and function as a mediator of Chk1 phosphorylation in response to DNA damage.

• Journal of Ginseng Research
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• v.46 no.4
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• pp.572-584
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• 2022

Background: Huntington's disease (HD) is a neurodegenerative disorder caused by the expansion of trinucleotide CAG repeat in the Huntingtin (Htt) gene. The major pathogenic pathways underlying HD involve the impairment of cellular energy homeostasis and DNA damage in the brain. The protein kinase ataxia-telangiectasia mutated (ATM) is an important regulator of the DNA damage response. ATM is involved in the phosphorylation of AMP-activated protein kinase (AMPK), suggesting that AMPK plays a critical role in response to DNA damage. Herein, we demonstrated that expression of polyQ-expanded mutant Htt (mHtt) enhanced the phosphorylation of ATM. Ginsenoside is the main and most effective component of Panax ginseng. However, the protective effect of a ginsenoside (compound K, CK) in HD remains unclear and warrants further investigation. Methods: This study used the R6/2 transgenic mouse model of HD and performed behavioral tests, survival rate, histological analyses, and immunoblot assays. Results: The systematic administration of CK into R6/2 mice suppressed the activation of ATM/AMPK and reduced neuronal toxicity and mHTT aggregation. Most importantly, CK increased neuronal density and lifespan and improved motor dysfunction in R6/2 mice. Conversely, CK enhanced the expression of Bcl2 protected striatal cells from the toxicity induced by the overactivation of mHtt and AMPK. Conclusions: Thus, the oral administration of CK reduced the disease progression and markedly enhanced lifespan in the transgenic mouse model (R6/2) of HD.

• Radiation Oncology Journal
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• v.12 no.1
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• pp.1-8
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• 1994

When cells are exposed to low doses of a mutagenic or clastogenic agents. they often become less sensitive to the effects of a higher dose administered subsequently. Such adaptive responses were first described in Escherichia coli and mammalian cells to low doses of an alkylating agent. Since most of the studies have been carried out with human lymphocytes, it is urgently necessary to study this effect in different cellular systems. Its relation with inherent cellular radiosensitivity and underlying mechanism also remain to be answered. In this study, adaptive response by 1 cGy of gamma rays was investigated in three human lymphoblastoid cell lines which were derived from ataxia telangiectasia homozygote, ataxia telangiectasia heterozygote, and normal individual. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher dose (50 cGy), The expression of this adaptive response was similar among three cell lines despite of their different radiosensitivity. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the tested cell lines. Therefore it is suggested that the adaptive response can be observed in human lymphoblastoid cell lines, which was first documented through this study. The expression of adaptive response was similar among the cell lines regardless of their radiosensitivity. The elimination of the adaptive response by 3-aminobenzamide is consistent with the proposal that this adaptive response is the result of the induction of a certain chromosomal repair mechanism.

• Proceedings of the Korean Biophysical Society Conference
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• 1999.06a
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• pp.69-69
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• 1999

The human genetic disorder ataxia-telangiectasia (A-T) is a multisystem disease characterized by extreme radiosensitivity. The recent identification of the gene mutated in A-T, ATM, and the demonstration that it encodes a homologous of phosphatidylinositol 3-kinase (PI3-K), the catalytic subunit of an enzyme involved in transmitting signals from the cell surface to the nucleus, provides support for a role for this gene in signal transduction.(omitted)

• Radiation Oncology Journal
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• v.17 no.4
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• pp.299-306
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• 1999

Purpose : The human genetic disorder ataxia-telangiectasia (AT) is a multisystem disease characterized by extreme radiosensitivity. The recent identification of the gene mutated in AT, ATM, and the demonstration that it encodes a homologous domain of phosphatidylinositol 3-kinase (PI3-K), the catalytic subunit of an enzyme involved in transmitting signals from the cell surface to the nucleus, provide support for a role of this gene in signal transduction. Although ionizing radiation was known to induce c-fos transcription, nothing is known about how ATM or PKCI mediated signal transduction pathway modulates the c-fos gene transcription and gene expression. Here we have studied the effect of PKCI on radiation sensitivity and c-fos transcription in normal and AT cells. Materials and Methods: Normal (LM217) and AT (AT5BIVA) cells were transfected with PKCI expression plasmid and the overexpression and integration of PKCI was evaluated by northern blotting and polymerase chain reaction, respectively. 5 Gy of radiation was exposed to LM and AT cells transfected with PKCI expression plasmid and cells were harvested 48 hours after radiation and investigated apoptosis with TUNEL method. The c-fos transcription activity was studied by performing CAT assay of reporter gene after transfection of c-fos CAT plasmid into AT and LM cells. Results: Our results demonstrate for the first time a role of PKCI on the radiation sensitivity and c-fos expression in LM and AT cells. PKCI increased radiation induced apoptosis in LM cells but reduced apoptosis in AT cells. The basal c-fos transcription activity is 70 times lower in AT cells than that in LM cells. The c-fos transcription activity was repressed by overexpression of PKCI in LM cells but not in AT cells. After induction of c-fos by Ras protein, overexpression of PKCI repressed c-fos transcription in LM cells but not in AT cells Conclusion: Overexpression of PKCI increased radiation sensitivity and repressed c-fos transcription in LM cells but not in AT cells. The results may be a. reason of increased radiation sensitivity of AT cells. PKCI may be involved in an ionizing radiation induced signal transduction pathway responsible for radiation sensitivity and c-fos transcription. The data also provided evidence for novel transcriptional difference between LM and AT cells.