Inhibition of UV-induced G1 arrest by exposure to 50 Hz magnetic fields in repair-proficient and -deficient yeast strains.
OBJECTIVE
To assess the possibility that extremely low frequency (ELF) magnetic fields obstruct the damage repair process, the gene conversion frequency and cell cycle kinetics in a DNA repair-proficient and nucleotide excision repair (NER)-deficient strain of diploid yeast Saccharomyces cerevisiae.


METHODS
DNA repair- or NER-deficient cells were irradiated with sublethal doses of ultraviolet light (UV) radiation followed by exposure to 50 Hz magnetic fields up to 30 mT for 48 h. After exposure, colony-forming ability was scored as revertants in which gene conversion had restored the functional allele of the ARG4 gene conversion hotspot. Cell cycle analysis was performed using flow cytometry.


RESULTS
Gene conversion rate was increased by the combined exposure in DNA repair-proficient cells, whereas it remained unchanged between UV alone and the combined exposure in NER-deficient cells. The UV-induced G1 arrest was inhibited by exposure to 30 mT ELF magnetic fields in both repair-proficient and -deficient cells.


CONCLUSIONS
The results suggest that exposure to high-density (30 mT) ELF magnetic fields decreases the efficiency of NER by suppressing G1 arrest, which in turn led to enhancement of the UV-induced gene conversion.
Takashima
Y
Y
Biotechnology Laboratory Railway Technical Research Institute, Hikaricho 2-8-38 Kokubunji, Tokyo 185-8540, Japan.
Ikehata
M
M
Miyakoshi
J
J
Koana
T
T
D002453:Cell Cycle / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D005434:Flow Cytometry; D016193:G1 Phase / Q000528:radiation effects*; D007700:Kinetics; D008280:Magnetics; D012441:Saccharomyces cerevisiae / Q000528:radiation effects; D013997:Time Factors; D014466:Ultraviolet Rays