Mitochondria and Radiation Damage

Tuesday, October 18, 2005 10:15 AM-12:00 PM Room No. 601
Chair(s): Pogozelski, Wendy; Hill, Helene

(SY037) Radiation and mitochondrial DNA deletions.

Pogozelski, Wendy1, Steinberg, Mark2, Hubbard, Karen3, Orlow, Irene4, Dermody, James5, Hill, Helene*,5, 1 Department of Chemistry, Geneseo, NY, US2 Department of Chemistry, New York, NY, US3 Department of Biology, New York, NY, US4 Epidemiology and Biostatistics Department, New York, NY, US5 Department of Microbiology and Molecular Genetics, Newark, NJ, US

ABSTRACT- Introduction and objectives: The advent of polymerase chain reaction (PCR) at the end of the last century has led to the development of ways to measure genes and gene expression present in extremely low amounts against high backgrounds of unrelated genetic material. The technique has been further refined by the advent of quantitative real-time PCR. The method of Pogozelski, et al. (Mitochondrion 2: 415, 2003) goes beyond that technique by allowing the determination of numbers of amplicons in a DNA sample relative to known numbers of the same amplicons in plasmids, thus permitting quantitation of PCR products approaching the level of single molecules. The goal of these studies has been to compare levels of total mitochondria and the mitochondrial common deletion – a lesion demonstrated to be related to reactive oxygen species and sun exposure – in human skin samples and in solar and gamma ray irradiated cultured human fibroblasts and keratinocytes. Results: While the common deletion is found in most of the 40 skin samples analyzed, it is present at far less than 1 copy per cell except for 6 samples which vary from 1 to 40 copies per cell. Total mitochondria vary from less than 1 per cell to over 5000 per cell in the 40 samples. In cultured cells the common deletion increases with radiation dose but is not expressed until several hours after exposure. In the course of these studies, new deletions in the region of the common deletion have been discovered that require a novel deletion mechanism involving intrastrand recombination at Hoogsteen 4-base paired motifs. Conclusions: Quantitative studies have permitted the elucidation of hitherto unexpected variations in mitochondrial numbers and allow detection and quantitation of reactive oxygen-species damage at the level of close to or at single mitochondria.–

Key words: quantitative pcr, reactive oxygen species damage, mitochondrial deletions

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2005 RRS