title: Impact of thymine glycol damage on DNA duplex energetics: Correlations with lesion-induced biochemical and structural consequences.
abstract: The magnitude and nature of lesion-induced energetic perturbations empirically correlate with mutagenicity/cytotoxicity profiles and can be predictive of lesion outcomes during polymerase-mediated replication in vitro. In this study, we assess the sequence and counterbase-dependent energetic impact of the Thymine glycol (Tg) lesion on a family of deoxyoligonucleotide duplexes. Tg damage arises from thymine and methyl-cytosine exposure to oxidizing agents or radiation-generated free-radicals. The Tg lesion blocks polymerase-mediated DNA replication in vitro and the unrepaired site elicits cytotoxic lethal consequences in vivo. Our combined calorimetric and spectroscopic characterization correlates Tg -induced energetic perturbations with biological and structural properties. Specifically, we incorporate a 5R-Tg isomer centered within the tridecanucleotide sequence 5'-GCGTACXCATGCG-3' (X = Tg or T) which is hybridized with the corresponding complementary sequence 5'-CGCATGNGTACGC-3' (N = A, G, T, C) to generate families of Tg -damaged (Tg ·N) and lesion-free (T·N) duplexes. We demonstrate that the magnitude and nature of the Tg destabilizing impact is dependent on counterbase identity (i.e., A ∼ G < T < C). The observation that a Tg lesion is less destabilizing when positioned opposite purines suggests that favorable counterbase stacking interactions may partially compensate lesion-induced perturbations. Moreover, the destabilizing energies of Tg ·N duplexes parallel their respective lesion-free T·N mismatch counterparts (i.e., G < T < C). Elucidation of Tg-induced destabilization relative to the corresponding undamaged mismatch energetics allows resolution of lesion-specific and sequence-dependent impacts. The Tg-induced energetic perturbations are consistent with its replication blocking properties and may serve as differential recognition elements for discrimination by the cellular repair machinery.
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, Piscataway, NJ, 08854.
authors.forename: Conceição A S A
authors.initials: CA
authors.lastname: Minetti
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, Piscataway, NJ, 08854.
authors.forename: David P
authors.initials: DP
authors.lastname: Remeta
authors.affiliation: Department of Pharmacological Sciences, School of Medicine, Stony Brook University, Stony Brook, NY, 11794.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Iden
authors.affiliation: Department of Pharmacological Sciences, School of Medicine, Stony Brook University, Stony Brook, NY, 11794.
authors.forename: Francis
authors.initials: F
authors.lastname: Johnson
authors.affiliation: Department of Pharmacological Sciences, School of Medicine, Stony Brook University, Stony Brook, NY, 11794.
authors.forename: Arthur P
authors.initials: AP
authors.lastname: Grollman
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, Piscataway, NJ, 08854.|Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, 08901.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Breslauer
mesh_terms: D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D004249:DNA Damage / Q000235:genetics; D009690:Nucleic Acid Conformation; D013816:Thermodynamics; D013941:Thymine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C029389:thymine glycol; D004247:DNA; D013941:Thymine
keywords: DNA damage; differential scanning calorimetry; mismatches; thermodynamics; thymidine glycol; thymine glycol