Oxidative guanine base damage regulates human telomerase activity

• Published in: Nature structural & molecular biology Vol. 23; no. 12; pp. 1092 - 1100
• Main Authors: Fouquerel, Elise, Lormand, Justin, Bose, Arindam, Lee, Hui-Ting, Kim, Grace S, Li, Jianfeng, Sobol, Robert W, Freudenthal, Bret D, Myong, Sua, Opresko, Patricia L
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01-12-2016; Nature Publishing Group
• Subjects: 631/337/1427/1979; 631/45/173; 631/80/103; Analysis; Base Sequence; Biochemistry; Biological Microscopy; Cancer; Cell Death; Cell Line; Cell Line, Tumor; Chromosomes; Damage; Degenerative diseases; Deoxyguanine Nucleotides - chemistry; Deoxyguanine Nucleotides - metabolism; Deoxyribonucleic acid; Depletion; DNA; DNA - chemistry; DNA - metabolism; DNA Adducts - chemistry; DNA Adducts - metabolism; DNA Damage; DNA structure; Elongated structure; Enzyme Activation; Enzymes; Free radicals; G-Quadruplexes; Genetic aspects; Guanine; Humans; Lesions; Life Sciences; Membrane Biology; Mutagens - chemistry; Mutagens - metabolism; Nucleotide sequence; Nucleotides; Oxidation-Reduction; Oxidative Stress; Physiological aspects; Protein Structure; Telomerase; Telomerase - metabolism; Telomere - chemistry; Telomere - metabolism; Telomere Shortening; Telomeres; Yeast; United States
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/nsmb.3319

Opposing effects of 8-oxodGTP on telomerase activity – promoting elongation by destabilizing G4 structures or inhibiting elongation by acting as a chain terminator – explain the differential sensitivity of cells with short telomeres to oxidative stress.
Changes in telomere length are associated with degenerative diseases and cancer. Oxidative stress and DNA damage have been linked to both positive and negative alterations in telomere length and integrity. Here we examined how the common oxidative lesion 8-oxo-7,8-dihydro-2′-deoxyguanine (8-oxoG) regulates telomere elongation by human telomerase. When 8-oxoG is present in the dNTP pool as 8-oxodGTP, telomerase utilization of the oxidized nucleotide during telomere extension is mutagenic and terminates further elongation. Depletion of MTH1, the enzyme that removes oxidized dNTPs, increases telomere dysfunction and cell death in telomerase-positive cancer cells with shortened telomeres. In contrast, a preexisting 8-oxoG within the telomeric DNA sequence promotes telomerase activity by destabilizing the G-quadruplex DNA structure. We show that the mechanism by which 8-oxoG arises in telomeres, either by insertion of oxidized nucleotides or by direct reaction with free radicals, dictates whether telomerase is inhibited or stimulated and thereby mediates the biological outcome.