Characterization of oxidative guanine damage and repair in mammalian telomeres

• Published in: PLoS genetics 2010-05, Vol.6 (5), p.e1000951-e1000951
• Main Authors: Wang, Zhilong, Rhee, David B, Lu, Jian, Bohr, Christina T, Zhou, Fang, Vallabhaneni, Haritha, de Souza-Pinto, Nadja C, Liu, Yie
• Format: Article
• Language: English
• Subjects: Animals; BASIC BIOLOGICAL SCIENCES; Bone marrow; Cell Biology/Cell Growth and Division; Cells, Cultured; Chromosomes; Deoxyribonucleic acid; DNA; DNA damage; Fluorescent Antibody Technique, Indirect; Genetics & Heredity; Genetics and Genomics/Animal Genetics; Genetics and Genomics/Cancer Genetics; Genetics and Genomics/Chromosome Biology; Genetics and Genomics/Disease Models; Genetics and Genomics/Genetics of Disease; Genetics and Genomics/Genomics; Guanine - chemistry; Guanosine - analogs & derivatives; Guanosine - chemistry; In Situ Hybridization, Fluorescence; Mice; Mice, Inbred C57BL; Mice, Knockout; Molecular Biology/Chromosome Structure; Molecular Biology/DNA; Molecular Biology/DNA Repair; Molecular Biology/Recombination; Oxidation-Reduction; Oxidative Stress; Proteins; Recombination, Genetic; Sister Chromatid Exchange; Telomere
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1000951

8-oxo-7,8-dihydroguanine (8-oxoG) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG) are among the most common oxidative DNA lesions and are substrates for 8-oxoguanine DNA glycosylase (OGG1)-initiated DNA base excision repair (BER). Mammalian telomeres consist of triple guanine repeats and are subject to oxidative guanine damage. Here, we investigated the impact of oxidative guanine damage and its repair by OGG1 on telomere integrity in mice. The mouse cells were analyzed for telomere integrity by telomere quantitative fluorescence in situ hybridization (telomere-FISH), by chromosome orientation-FISH (CO-FISH), and by indirect immunofluorescence in combination with telomere-FISH and for oxidative base lesions by Fpg-incision/Southern blot assay. In comparison to the wild type, telomere lengthening was observed in Ogg1 null (Ogg1(-/-)) mouse tissues and primary embryonic fibroblasts (MEFs) cultivated in hypoxia condition (3% oxygen), whereas telomere shortening was detected in Ogg1(-/-) mouse hematopoietic cells and primary MEFs cultivated in normoxia condition (20% oxygen) or in the presence of an oxidant. In addition, telomere length abnormalities were accompanied by altered telomere sister chromatid exchanges, increased telomere single- and double-strand breaks, and preferential telomere lagging- or G-strand losses in Ogg1(-/-) mouse cells. Oxidative guanine lesions were increased in telomeres in Ogg1(-/-) mice with aging and primary MEFs cultivated in 20% oxygen. Furthermore, oxidative guanine lesions persisted at high level in Ogg1(-/-) MEFs after acute exposure to hydrogen peroxide, while they rapidly returned to basal level in wild-type MEFs. These findings indicate that oxidative guanine damage can arise in telomeres where it affects length homeostasis, recombination, DNA replication, and DNA breakage repair. Our studies demonstrate that BER pathway is required in repairing oxidative guanine damage in telomeres and maintaining telomere integrity in mammals.