MNNG所致哺乳类细胞非定标性突变的时相分析

Phasic analysis of MNNG induced nontargeted mutation in mammalian cells

On the basis of the evidence for nontargeted mutagenesis in mammalian cells acquired in our laboratory, the mechanism of mutation was studied. lntact shuttle vector pZ189 DNA was allowed to replicate in monkey kidney vero cells at various times, i.e. 3, 6, 12, 24, 36 and 48 h after the cells were#O&;treated with 0.2 μmol·L^-1 N-methyl-N’-nitro-N- nitrosoguanidine (MNNG). The E. coli MBM 7070 was transformed with replicated plasmid, and those with mutations in the supF tRNA gene were identified. DMSO, the solvent of MNNG was served as control simultaneously at each time group. Compared with the control, the increasing mutation frequency was found at 6 h and 12 h after MNNG exposure, with the relative ratio of MNNG induced and spontaneous mutation rate was 4.42 (P<0.01) and 5.44 (P<0.01) respectively. The dynamic behavior of mutation frequency accorded with the metabolic characteristic of proteins and suggested that newly synthetic proteins would be required in the process of nontargeted mutation formation in mammalian cells.