Analysis of large deletion mutations induced by abasic site analog in human cells

BACKGROUND: Abasic sites are formed spontaneously and by nucleobase chemical modifications and base excision repair. A chemically stable abasic site analog was site-specifically introduced into replicable plasmid DNAs, which were transfected into human U2OS cells. The amplified DNAs were recovered from the cells and used for the transformation of a bacterial indicator strain. RESULTS: Large deletion mutations were induced by the analog, in addition to point mutations at the modified site. No apparent sequence homology at the deletion junctions was found. CONCLUSION: These results suggested that the large deletions induced by the abasic site analog are formed by homology-independent events.