DEFICIENT DNA-REPAIR OF TRIPLE HELIX-DIRECTED DOUBLE PSORALEN DAMAGE IN HUMAN-CELLS

Damage induced by a single psoralen-modified triple helix-forming olig onucleotide has been reported to be efficiently repaired in human cell s, In this study we investigated a set of psoralen coupled oligonucleo tides introducing multiple lesions into the target DNA. A simian virus 40 (SV40) shuttle vector was in vitro treated with different triple h elix-forming oligonucleotides and UVA radiation, leading to double pso ralen adducts at the supF mutational target gene of the plasmid, After passage in the Rail human cell line the recovered vector was analysed in an indicator bacterial strain, The results show that double psoral en adducts, located at both ends of a long triple helix, cannot be rep aired efficiently in human cells.