Psoralens cleave pBR322 DNA under ultraviolet radiation.
Supercoiled (SC) pBR322 was used to probe the recent claim that 5-geranoxylpsoralen (5-GOP) did not photoreact with DNA. Contrary to expectations, 5-GOP was found to damage DNA in the presence of UV-A through two competing pathways: (a) single strand breaks, identified by the conversion of supercoiled into open circular and linear DNA, and (b) cross-linking, revealed by the fluence-dependent decrease in the extent of denaturation of the double stranded supercoiled DNA to single stranded circular DNA. In addition, a fluence-dependent modification reduced the ability of the restriction enzyme EcoR I to linearize the photosensitized DNA, and alkali-labile lesions were generated. Psoralen, 5-methoxypsoralen, and 8-methoxypsoralen, which are well-known to undergo cycloaddition to DNA, had a more pronounced effect on supercoiled DNA. Single strand breaks occurred more readily than with 5-GOP, and the surviving SC form remaining had reduced electrophoretic mobility in agarose gels. In all cases, the DNA damage was more prominent when oxygen was absent.
Kagan
J
J
Department of Chemistry, University of Illinois, Chicago 60680.
Chen
X
X
Wang
T P
TP
Forlot
P
P
D004278:DNA, Superhelical / Q000187:drug effects* / Q000528:radiation effects*; D011564:Furocoumarins / Q000737:chemistry / Q000494:pharmacology*; D015394:Molecular Structure; D010777:Photochemistry; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D014466:Ultraviolet Rays
D004278:DNA, Superhelical; D011564:Furocoumarins; D011838:Radiation-Sensitizing Agents; C068337:bergamottin