Targeted and Persistent 8-Oxoguanine Base Damage at Telomeres Promotes Telomere Loss and Crisis

• DOI: 10.1016/j.molcel.2019.04.024
• Publication Date: 2019-05-14T14:29:33Z
• Authors: Elise Fouquerel; Ryan P. Barnes; Shikhar Uttam; Simon C. Watkins; Marcel P. Bruchez; Patricia L. Opresko
• Keywords: Chromosome Aberrations; DNA Replication; 0301 basic medicine; Guanine; Osteoblasts; DNA Repair; Light; Singlet Oxygen; Cell Survival; Gene Expression; Telomere; Genomic Instability; DNA Glycosylases; Optogenetics; Oxidative Stress; 03 medical and health sciences; Cell Line, Tumor; Humans; Cell Division; Micronuclei, Chromosome-Defective; DNA Damage; HeLa Cells

Telomeres are essential for genome stability. Oxidative stress caused by excess reactive oxygen species (ROS) accelerates telomere shortening. Although telomeres are hypersensitive to ROS-mediated 8-oxoguanine (8-oxoG) formation, the biological effect of this common lesion at telomeres is poorly understood because ROS have pleiotropic effects. Here we developed a chemoptogenetic tool that selectively produces 8-oxoG only at telomeres. Acute telomeric 8-oxoG formation increased telomere fragility in cells lacking OGG1, the enzyme that removes 8-oxoG, but did not compromise cell survival. However, chronic telomeric 8-oxoG induction over time shortens telomeres and impairs cell growth. Accumulation of telomeric 8-oxoG in chronically exposed OGG1-deficient cells triggers replication stress, as evidenced by mitotic DNA synthesis at telomeres, and significantly increases telomere losses. These losses generate chromosome fusions, leading to chromatin bridges and micronucleus formation upon cell division. By confining base damage to the telomeres, we show that telomeric 8-oxoG accumulation directly drives telomere crisis.