title: Alkali reversal of psoralen cross-link for the targeted delivery of psoralen monoadduct lesion.
abstract: Psoralen intercalates into double-stranded DNA and photoreacts mainly with thymines to form monoadducts and interstrand cross-links. We used an oligonucleotide model to demonstrate a novel mechanism: the reversal of psoralen cross-links by base-catalyzed rearrangement at 90 degrees C (BCR). The BCR reaction is more efficient than the photoreversal reaction. We show that the BCR occurs predominantly on the furan side of a psoralen cross-link. The cleavage does not result in the breaking of the DNA backbone, and the thymine base freed from the cross-link by the cleavage reaction appears to be unmodified. Similarly, BCR of the furan-side monoadduct of psoralen removed the psoralen molecule and regenerated the unaltered native oligonucleotide. The pyrone-side psoralen monoadduct is relatively resistant to BCR. One can use BCR to perform efficient oligonucleotide-directed, site-specific delivery of a psoralen monoadduct. As a demonstration of this approach, we have hybridized a 19 base long oligonucleotide vehicle containing a furan-side psoralen monoadduct to a 56 base long complementary oligonucleotide target strand and formed a specific cross-link at the target site with 365-nm UV. Subsequent BCR released the oligonucleotide vehicle and deposited the psoralen at the target site.
authors.affiliation: Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111.
authors.forename: A T
authors.initials: AT
authors.lastname: Yeung
authors.forename: W J
authors.initials: WJ
authors.lastname: Dinehart
authors.forename: B K
authors.initials: BK
authors.lastname: Jones
mesh_terms: D001483:Base Sequence; D003432:Cross-Linking Reagents; D004247:DNA / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage; D011564:Furocoumarins; D006863:Hydrogen-Ion Concentration; D009838:Oligodeoxyribonucleotides; D010777:Photochemistry; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D011564:Furocoumarins; D009838:Oligodeoxyribonucleotides; D004247:DNA