title: Radical-induced purine lesion formation is dependent on DNA helical topology.
abstract: Herein we report the quantification of purine lesions arising from gamma-radiation sourced hydroxyl radicals (HO•) on tertiary dsDNA helical forms of supercoiled (SC), open circular (OC), and linear (L) conformation, along with single-stranded folded and non-folded sequences of guanine-rich DNA in selected G-quadruplex structures. We identify that DNA helical topology and folding plays major, and unexpected, roles in the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) and 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxo-dA), along with tandem-type purine lesions 5',8-cyclo-2'-deoxyguanosine (5',8-cdG) and 5',8-cyclo-2'-deoxyadenosine (5',8-cdA). SC, OC, and L dsDNA conformers together with folded and non-folded G-quadruplexes d[TGGGGT]4(TG4T), d[AGGG(TTAGGG)3] (Tel22), and the mutated tel24 d[TTGGG(TTAGGG)3A] (mutTel24) were exposed to HO•radicals and purine lesions were then quantified via stable isotope dilution LC-MS/MS analysis. Purine oxidation in dsDNA follows L > OC ≫ SC indicating greater damage towards the extended B-DNA topology. Conversely, G-quadruplex sequences were significantly more resistant toward purine oxidation in their unfolded states as compared with G-tetrad folded topologies; this effect is confirmed upon comparative analysis of Tel22 (∼50% solution folded) and mutTel24 (∼90% solution folded). In an effort to identify the accessibly of hydroxyl radicals to quadruplex purine nucleobases, G-quadruplex solvent cavities were then modeled at 1.33 Å with evidence suggesting that folded G-tetrads may act as potential oxidant traps to protect against chromosomal DNA damage.
authors.affiliation: a ISOF , Consiglio Nazionale delle Ricerche , Bologna , Italy.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Terzidis
authors.affiliation: b School of Chemical Sciences and National Institute for Cellular Biotechnology , Dublin City University , Glasnevin , Dublin , Ireland.
authors.forename: Andreea
authors.initials: A
authors.lastname: Prisecaru
authors.affiliation: b School of Chemical Sciences and National Institute for Cellular Biotechnology , Dublin City University , Glasnevin , Dublin , Ireland.
authors.forename: Zara
authors.initials: Z
authors.lastname: Molphy
authors.affiliation: b School of Chemical Sciences and National Institute for Cellular Biotechnology , Dublin City University , Glasnevin , Dublin , Ireland.
authors.forename: Niall
authors.initials: N
authors.lastname: Barron
authors.affiliation: c Department of Pharmacy , University of Naples "Federico II" , Napoli , Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Randazzo
authors.affiliation: d Laboratoire de Chimie, UMR 5182 CNRS , École Normale Supérieure de Lyon , Lyon Cedex , France.
authors.forename: Elise
authors.initials: E
authors.lastname: Dumont
authors.affiliation: e NCSR "Demokritos" , Institute of Nanoscience and Nanotechnology , Athens , Greece.
authors.forename: Marios G
authors.initials: MG
authors.lastname: Krokidis
authors.affiliation: b School of Chemical Sciences and National Institute for Cellular Biotechnology , Dublin City University , Glasnevin , Dublin , Ireland.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kellett
authors.affiliation: a ISOF , Consiglio Nazionale delle Ricerche , Bologna , Italy.|e NCSR "Demokritos" , Institute of Nanoscience and Nanotechnology , Athens , Greece.
authors.forename: Chryssostomos
authors.initials: C
authors.lastname: Chatgilialoglu
mesh_terms: D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D017665:Hydroxyl Radical / Q000737:chemistry*; D010084:Oxidation-Reduction; D011687:Purines / Q000737:chemistry*
chemical_list: D011687:Purines; D017665:Hydroxyl Radical; D004247:DNA; C030985:purine
keywords: Cyclonucleoside; DNA oxidation; G-quadruplex; hydroxyl radical; superhelix