Induction of a Particular Deletion in Mitochondrial DNA by X Rays Depends on the Inherent Radiosensitivity of the Cells

Kubota, Nobuo; Hayashi, Jun‐Ichi; Inada, Tomohiro; Iwamura, Yukio

doi:10.2307/3579525

Cited by 36 publications

(21 citation statements)

References 22 publications

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“…The second round of PCR employed the inner primer set F3 and R3, and an additional 20 cycles were run at 94°C for 30 s for denaturation, 60°C for 25 s for annealing, and 72°C for 25 s for extension. For detection of very small amounts of deletion mutant mtDNA molecules, the primer set F2 and R2 was used in the second round, and the primer set F3 and R3 was used in the last round (18). The amplified products were separated in 2.5% agarose gels containing ethidium bromide (0.1 g/ml).…”

Section: Cells and Cell Culture-normalmentioning

confidence: 99%

Nuclear-recessive Mutations of Factors Involved in Mitochondrial Translation Are Responsible for Age-related Respiration Deficiency of Human Skin Fibroblasts

Isobe¹,

Ito²,

Hosaka³

et al. 1998

Journal of Biological Chemistry

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We addressed the question of whether both mitochondrial and cytoplasmic translation activities decreased simultaneously in human skin fibroblasts with the age of the donors and found that the age-related reduction was limited to mitochondrial translation. Then, to determine which genome, mitochondrial or nuclear, was responsible for this age-related, mitochondria-specific reduction, pure nuclear transfer was carried out from mitochondrial DNA (mtDNA)-less HeLa cells to four fibroblast lines, two from aged subjects, one from a fetus, and one from a patient with cardiomyopathy, and their nuclear hybrid clones were isolated. A normal fibroblast line from the fetus and a respiration-deficient fibroblast line from the patient were used as a positive and a negative control, respectively. Subsequently, the mitochondrial translation and respiration properties of the nuclear hybrid clones were compared. A negative control experiment showed that this procedure could be used to isolate even nuclear hybrids expressing overall mitochondrial respiration deficiency, whereas no respiration deficiencies were observed in any nuclear hybrids irrespective of whether their mtDNAs were exclusively derived from aged or fetal donors. These observations suggest that nuclear-recessive mutations of factors involved in mitochondrial translation but not mtDNA mutations are responsible for age-related respiration deficiency of human fibroblasts.It has been presumed that somatic mutations accumulate in mitochondrial DNA (mtDNA) much faster than in nuclear DNA because mitochondria are highly oxygenic organelles due to their function in producing energy, mtDNA lacks histones protecting it from mutagenic damage, and its repair systems are limited (1). Therefore, it has been proposed that the accumulation of various somatic mutations in mtDNA and the resultant decrease in mitochondrial respiratory function could be involved in aging processes in mammals (2-4). There have been many reports that the respiration capacity of mitochondria in highly oxidative tissues decreases during aging (4). Moreover, the accumulation of somatic and pathogenic mtDNA mutations, which have been shown to cause various kinds of mitochondrial encephalomyopathies (5-8), was also shown to increase with age in normal subjects (9, 10). However, as the nuclear genome encodes most mitochondrial proteins including factors necessary for replication and expression of the mitochondrial genome, it is possible that only mutations in the nuclear genome contribute to the age-related decline of mitochondrial respiratory function. In fact, there is no convincing evidence that mtDNA somatic mutations are responsible for this age-related phenotype.Previously, we observed age-related reduction of cytochrome c oxidase (COX) 1 activity and mitochondrial translation in cultured human skin fibroblasts isolated from donors of various ages (0 -97 years), and in studies on their mtDNA transfer to mtDNA-less ( 0 ) HeLa cells, we showed that mtDNA mutations were not responsible for the observed age...

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Section: Cells and Cell Culture-normalmentioning

confidence: 99%

Nuclear-recessive Mutations of Factors Involved in Mitochondrial Translation Are Responsible for Age-related Respiration Deficiency of Human Skin Fibroblasts

Isobe¹,

Ito²,

Hosaka³

et al. 1998

Journal of Biological Chemistry

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“…Excited oxygen species (e.g., the superoxide radical, hydrogen peroxide and hydroxyl radical) are formed during aerobic metabolism and exposure to ionizing radiation, which is a potent genotoxic factor that may contribute to the excessive mutagenesis of nucleic acids. Thus, mtDNA could be particularly sensitive to ionizing radiation [5,8]. Consistent with this notion, both point mutations and large-scale deletions in mtDNA are known to arise after exposure to ionizing radiation [5,9,10].…”

Section: Introductionmentioning

confidence: 75%

“…Since 95% of mtDNA is coding (versus only 3% of nuclear DNA), any damage on mtDNA is likely to affect a coding region [3]. In addition, mtDNA lacks protective histones and does not have an effective DNA repair system [4,5]. Within a given cell, the mtDNA may be a mix of both wild-type and mutant genotypes; this is known as heteroplasmy.…”

Section: Introductionmentioning

confidence: 96%

Detection and quantification of a radiation-associated mitochondrial DNA deletion by a nested real-time PCR in human peripheral lymphocytes

Kim¹,

Kim²,

Yun³

et al. 2012

Mutation Research/Genetic Toxicology and Environmental Mutagene

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“…Perhaps the strongest evidence comes from a study which used x-rays to induce the deletion in cultured cells. That the level of induction varied with cell type, and that the deletion was induced at all, are both of great interest (112).…”

Section: Relationship Between Deletions and Oxidative Damagementioning

confidence: 99%

Mitochondria, oxidative DNA damage, and aging

Anson

Bohr

2000

AGE

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Protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage is well known to be necessary to longevity. The relevance of mitochondrial DNA (mtDNA) to aging is suggested by the fact that the two most commonly measured forms of mtDNA damage, deletions and the oxidatively induced lesion 8-oxo-dG, increase with age. The rate of increase is species-specific and correlates with maximum lifespan.It is less clear that failure or inadequacies in the protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage are sufficient to explain senescence. DNA containing 8-oxo-dG is repaired by mitochondria, and the high ratio of mitochondrial to nuclear levels of 8-oxo-dG previously reported are now suspected to be due to methodological difficulties. Furthermore, MnSOD -/+ mice incur higher than wild type levels of oxidative damage, but do not display an aging phenotype. Together, these findings suggest that oxidative damage to mitochondria is lower than previously thought, and that higher levels can be tolerated without physiological consequence.A great deal of work remains before it will be known whether mitochondrial oxidative damage is a "clock" which controls the rate of aging. The increased level of 8-oxo-dG seen with age in isolated mitochondria needs explanation. It could be that a subset of cells lose the ability to protect or repair mitochondria, resulting in their incurring disproportionate levels of damage. Such an uneven distribution could exceed the reserve capacity of these cells and have serious physiological consequences.

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Induction of a Particular Deletion in Mitochondrial DNA by X Rays Depends on the Inherent Radiosensitivity of the Cells

Cited by 36 publications

References 22 publications

Nuclear-recessive Mutations of Factors Involved in Mitochondrial Translation Are Responsible for Age-related Respiration Deficiency of Human Skin Fibroblasts

Nuclear-recessive Mutations of Factors Involved in Mitochondrial Translation Are Responsible for Age-related Respiration Deficiency of Human Skin Fibroblasts

Detection and quantification of a radiation-associated mitochondrial DNA deletion by a nested real-time PCR in human peripheral lymphocytes

Mitochondria, oxidative DNA damage, and aging

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