Journal
JOURNAL OF CELL SCIENCE
Volume 125, Issue 22, Pages 5280-5287Publisher
COMPANY OF BIOLOGISTS LTD
DOI: 10.1242/jcs.101006
Keywords
DNA double-strand break repair; Unrepairable DSBs; Ionising radiation; Cell senescence; gamma H2AX
Categories
Funding
- Radiation Effects Research Foundation (RERF) [RP A4-09]
- Ministry of Education, Sports, Science and Technology (MEXT) of Japan [s-21221003]
- Japanese Ministry of Health, Labour and Welfare (MHLW)
- U.S. Department of Energy (DOE) through DOE Award [DE-HS0000031]
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After an exposure to ionising radiation, cells can quickly repair damage to their genomes; however, a few unrepairable DNA double-strand breaks (DSBs) emerge in the nucleus in a prolonged culture and perpetuate as long as the culture continues. These DSBs may be retained forever in cells such as non-dividing ageing tissues, which are resistant to apoptosis. We show that such unrepairable DSBs, which had been advocated by the classical target theory as the 'radiation hit', could account for permanent growth arrest and premature senescence. The unrepairable DSBs build up with repeated irradiation, which accounts for an accumulated dose. Because these DSBs tend to be paired, we propose that the untethered and 'torn-off' molecular structures at the broken ends of the DNA result in an alteration of chromatin structure, which protects the ends of the DNA from genomic catastrophe. Such biochemical responses are important for cell survival but may cause gradual tissue malfunction, which could lead to the late effects of radiation exposure. Thus, understanding the biology of unrepairable damage will provide new insights into the long-term effects of radiation.
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