Induction of chromosomal aberrations in the CHO mutant EM9 and its parental line AA8 by EcoRI restriction endonuclease: electroporation experiments

EcoRI restriction endonuclease (RE), which produces cohesive-ended double-strand breaks (dsb) in DNA, was tested in the ethyl methanesulfonate- and X-ray-sensitive CHO mutant EM9 and its parental cell strain AA8 for its chromosomal aberration-inducing effect. The RE was efficiently introduced by electroporation into AA8 cells, while the mutant cells showed a very high sensitivity to electroporation, which consistently resulted in cell death. Nevertheless, the incubation of EM9 cells in the presence of EcoRI, without electroporation, was sufficient to induce about three times the chromosome damage observed in the electroporated parental cell line AA8 for any given dose of the RE.