Abstract
This study is intended to elucidate the mechanism of the mutagenesis by ion beam at molecular level. At first, survival rate and mutation frequency for the ion beam were obtained using yeast S288C. Next, mutation spectrum of mutants obtained by ion beam irradiation was measured by sequencing the mutation sites. S. cerevisiae strains used in this study are S288C(RAD+),rad3, rad18, and rad52.
The yeast strains were irradiated with carbon ions (12C5+; 220 MeV) with the dose 10 to 300 Gy, and LET is 107 keV/µm. Carbon ion beam was generated from AVF cyclotron in JAERI. The results indicated that rad52 strain showed high sensitivity to ion-beam, and that the optimum dose for mutagenesis was 100 Gy, and at the dose, mutation occurred 168.5 times more than spontaneous mutation. Moreover, The ura3 mutants were amplified by PCR, and the sequence analysis was carried out.
The result shows that mutations caused with ion beam irradiation have remarkable features and hot spots. Mutations of spontaneous generation tend to take the type of transition, and transversion is rare compared with transition. It was observed in this experiment that transversion was occurred by 5 times more than transition.
