title: Effect of sequence and metal ions on UVB-induced anti cyclobutane pyrimidine dimer formation in human telomeric DNA sequences.
abstract: Irradiation of G-quadruplex forming human telomeric DNA with ultraviolet B (UVB) light results in the formation of anti cyclobutane pyrimidine dimers (CPDs) between loop 1 and loop 3 in the presence of potassium ions but not sodium ions. This was unexpected because the sequences involved favor the nonphotoreactive hybrid conformations in K(+) solution, whereas a potentially photoreactive basket conformation is favored in Na(+) solution. To account for these contradictory results, it was proposed that the loops are too far apart in the basket conformation in Na(+) solution but close enough in a two G-tetrad basket-like form 3 conformation that can form in K(+) solution. In the current study, Na(+) was still found to inhibit anti CPD formation in sequences designed to stabilize the form 3 conformation. Furthermore, anti CPD formation in K(+) solution was slower for the sequence previously shown to exist primarily in the proposed photoreactive form 3 conformation than the sequence shown to exist primarily in a nonphotoreactive hybrid conformation. These results suggest that the form 3 conformation is not the principal photoreactive conformation, and that G-quadruplexes in K(+) solution are dynamic and able to access photoreactive conformations more easily than in Na(+) solution.
authors.affiliation: Department of Chemistry, Washington University, St. Louis, MO 63130, USA.
authors.forename: Jillian E
authors.initials: JE
authors.lastname: Smith
authors.forename: Chen
authors.initials: C
authors.lastname: Lu
authors.forename: John-Stephen
authors.initials: JS
authors.lastname: Taylor
mesh_terms: D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004247:DNA / Q000737:chemistry* / Q000528:radiation effects; D054856:G-Quadruplexes / Q000528:radiation effects; D006801:Humans; D009154:Mutation; D011188:Potassium / Q000737:chemistry*; D011740:Pyrimidine Dimers / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry; D013237:Stereoisomerism; D016615:Telomere / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D011740:Pyrimidine Dimers; D004247:DNA; D012964:Sodium; D011188:Potassium