The restriction endonuclease AluI induces sister chromatid exchange in Chinese hamster ovary cells

Abstract
Chinese hamster ovary (CHO) cells were exposed to the restriction endonuclease AluI in the presence of 1.1 M glycerol. Chromosomal aberrations and sister chromatid exchange (SCE) were scored in first post-treatment metaphases following recovery times of 6-18 h. At all recovery times chromosomal aberrations were induced by the enzyme. In AluI-treated damaged cells significant elevations of SCE frequencies were found after recovery times of 12-18 h. These results indicate that SCE, unlike chromosomal aberrations, are induced only in late G1 and early S phase of the cell cycle. The lesions producing SCE are postulated as DNA single-strand breaks and gaps induced by AluI in canonical structures of DNA and in DNA-RNA hybrids.

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