Telomere Dysfunction and DNA-PKcs Deficiency: Characterization and Consequence
Overview
Authors
Affiliations
The mechanisms by which cells accurately distinguish between DNA double-strand break (DSB) ends and telomeric DNA ends remain poorly defined. Recent investigations have revealed intriguing interactions between DNA repair and telomeres. We were the first to report a requirement for the nonhomologous end-joining (NHEJ) protein DNA-dependent protein kinase (DNA-PK) in the effective end-capping of mammalian telomeres. Here, we report our continued characterization of uncapped (as opposed to shortened) dysfunctional telomeres in cells deficient for the catalytic subunit of DNA-PK (DNA-PKcs) and shed light on their consequence. We present evidence in support of our model that uncapped telomeres in this repair-deficient background are inappropriately detected and processed as DSBs and thus participate not only in spontaneous telomere-telomere fusion but, importantly, also in ionizing radiation-induced telomere-DSB fusion events. We show that phosphorylation of DNA-PKcs itself (Thr-2609 cluster) is a critical event for proper telomere end-processing and that ligase IV (NHEJ) is required for uncapped telomere fusion. We also find uncapped telomeres in cells from the BALB/c mouse, which harbors two single-nucleotide polymorphisms that result in reduced DNA-PKcs abundance and activity, most markedly in mammary tissue, and are both radiosensitive and susceptible to radiogenic mammary cancer. Our results suggest mechanistic links between uncapped/dysfunctional telomeres in DNA-PKcs-deficient backgrounds, radiation-induced instability, and breast cancer. These studies provide the first direct evidence of genetic susceptibility and environmental insult interactions leading to a unique and ongoing form of genomic instability capable of driving carcinogenesis.
DNA-PK controls Apollo's access to leading-end telomeres.
Sonmez C, Toia B, Eickhoff P, Matei A, El Beyrouthy M, Wallner B Nucleic Acids Res. 2024; 52(8):4313-4327.
PMID: 38407308 PMC: 11077071. DOI: 10.1093/nar/gkae105.
The recent advances in non-homologous end-joining through the lens of lymphocyte development.
Wang X, Lee B, Zha S DNA Repair (Amst). 2020; 94:102874.
PMID: 32623318 PMC: 7885906. DOI: 10.1016/j.dnarep.2020.102874.
Helm J, Rudel R Arch Toxicol. 2020; 94(5):1511-1549.
PMID: 32399610 PMC: 7261741. DOI: 10.1007/s00204-020-02752-z.
DNA-PKcs has KU-dependent function in rRNA processing and haematopoiesis.
Shao Z, Flynn R, Crowe J, Zhu Y, Liang J, Jiang W Nature. 2020; 579(7798):291-296.
PMID: 32103174 PMC: 10919329. DOI: 10.1038/s41586-020-2041-2.
Al-Aamri H, Irving H, Meehan-Andrews T, Bradley C BMC Res Notes. 2019; 12(1):625.
PMID: 31551083 PMC: 6760046. DOI: 10.1186/s13104-019-4663-8.