Epidemiological studies suggest that extremely low frequency (ELF) magnetic fields (MF), which are generated from power transmission lines and other common electrical devices, can cause cancer. However, little laboratory data are available to either support or refute these findings, o define the critical biological targets or response of cells to these fields This proposal focuses on the identification of changes in protein synthesis profiles induced by ELF-MF exposure and the molecular mechanisms in control. The fission yeast Schizosaccharomyces pombe is used as a model system because it can serve as a sensitive tool to detect biological change induced by ELF-MF and to dissect the genetic basis for any alterations observed. Our initial studies were carried Out using the exposure device of Goodman and Henderson. Using 2-D gel electrophoresis, we found that synthesis of three proteins (of approximately 500 proteins detected by this procedure) was transiently turned off in wild-type S. pombe cells after exposure to a 60 Hz 80 mu T MF for 20 min. The fact that only three proteins were affected by this treatment demonstrates the high specificity of the molecular response. Furthermore, following the same treatment, yeast cells containing the checkpoint control gene mutation rad9::ura4 also transiently cease synthesis of two of these proteins, but continue to make the third, indicating that regulation of this latter protein is rad9-depend t and linked to cell cycle control. No new proteins were detected after ELF- MF treatment. These observations form the foundation for the current proposal. Studies in this application will be performed with a Magnacell MC-2xc ELF-MF system, which is currently used by the NIOSH and the EPA for investigation and meets all requirements set forth by the NIEHS to generate true MF of defined intensities while minimizing the production of electric fields. The specific goals of this proposal are to identify regulated yeast proteins, and isolate and characterize the genes encoding these proteins. Regulation in other S. pombe checkpoint control mutants, containing rad1-1, rad3-136 or rad17W, will be examined to test whether the rad9-dependent control is, in general, a checkpoint-related effect. The ability of ELF-MF to induce delay in S. pombe cells will also be examined. Synthesis of these proteins in heat-shocked and gamma- irradiated cells will be examined to test whether they are part of pathways that generally respond to insults. Studies will also be conducted to identi the gene regulatory sites. Together, the results of this study should ident y proteins regulated by ELF-MF and reveal the nature of the molecular mechanisms in control.
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