Use of a Bacterial Gene Expression System for Mutation Repairing (umu system) to evaluate Damage in DNA Molecules Resulting from Exposure to an Extra Low Frequency Magnetic Field

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Though there are many affirmative or negative reports on affect vicious of extremely low frequency magnetic field (ELFMF) exposure to human body, especially on the effect to oncogenesis, its conclusion has not been reached yet. Cells, which constitute the human body, suffer damage of DNA, and mutation is caused by mutagenic substances or phenomena. It is well known that mutation becomes a direct cause of cancer-developing, and there is a close relation between the oncogenesis of cells and molecular damage of DNA.In a meantime, genetic engineering has been developed remarkably, the experimental technique in DNA analysis has generally been adopted to the many fields of sciences. Therefore the gene level research of the import of the ELFMF exposure to the living cell can also be dove using molecular biological technique. When DNA of bacteria is damaged by some causes, SOS repairing genetic systems, for instance umu operon and recA genes, which intend to restore the damage, are expressed. In this study, the possibility of applying expression system of a SOS regulon by umu assay method, which clarifies the impact of a magnetic field exposure for gene mutation by a damage in DNA molecule, was examined. We exposed bacterium Salmonella typhimurium TA153(pSK1002) (a derivative strain whose pathogenicity was deleted) to ELFMF, and the intensity of the expression of an enzymatic activity of β-galactosidase which is the product of lacZ gene located downstream of the umu SOS gene operon, was examined by umu assay method with a non-exposure control. The experimental results showed that the umu assay could be effectively applied to the evaluation of damage in DNA molecules by exposure to an ELFMF.However, no significant differences were observed in the umu gene expression intensity under experimental condition.