title: Suppression of cyclobutane and mean value of 6-4 dipyrimidines formation in triple-stranded H-DNA.
abstract: We have determined the effect of H-DNA formation on the distributions of two ultraviolet (UV) light induced photoproducts--cyclobutane dipyrimidines and mean value of 6-4 dipyrimidines. A region of DNA containing the sequence (dT-dC)18.(dA-dG)18 was treated under conditions that specifically yield the triple-stranded H-y3 or H-y5 DNA structure and then irradiated with UV. The positions of cyclobutane dipyrimidines and mean value of 6-4 dipyrimidines were determined by T4 endonuclease V cleavage and by hot piperidine cleavage, respectively. Formation of H-DNA structures greatly decreased the photoproduct yield in the (dT-dC)18.(dA-dG)18 region but not elsewhere in the DNA. Suppression of photoproduct formation is greater in half of the repeat, reflecting whether the DNA is in the H-y3 or H-y5 conformation. Within the repeat, the suppression was less in the middle and toward the ends. Models for the suppression of photoproduct formation in H-DNA and the possible utility of our findings are discussed.
authors.affiliation: University of Texas M. D. Anderson Cancer Center, Science Park-Research Division, Smithville 78957.
authors.forename: M S
authors.initials: MS
authors.lastname: Tang
authors.forename: H
authors.initials: H
authors.lastname: Htun
authors.forename: Y
authors.initials: Y
authors.lastname: Cheng
authors.forename: J E
authors.initials: JE
authors.lastname: Dahlberg
mesh_terms: D001482:Base Composition / Q000528:radiation effects; D001483:Base Sequence / Q000528:radiation effects; D003503:Cyclobutanes / Q000737:chemistry*; D004247:DNA / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation / Q000528:radiation effects; D010880:Piperidines; D011740:Pyrimidine Dimers; D014466:Ultraviolet Rays
chemical_list: D003503:Cyclobutanes; D010880:Piperidines; D011740:Pyrimidine Dimers; C032727:piperidine; D004247:DNA