Nakamura Asako J, Redon Christophe E, Bonner William M, Sedelnikova Olga A
Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Aging (Albany NY). 2009 Feb 4;1(2):212-8. doi: 10.18632/aging.100019.
Human tumors and cultured cells contain elevated levels of endogenous DNA damage resulting from telomere dysfunction, replication and transcription errors, reactive oxygen species, and genome instability. However, the contribution of telomere-associated versus telomere-independent endogenous DNA lesions to this damage has never been examined. In this study, we characterized the relative amounts of these two types of DNA damage in five tumor cell lines by noting whether gamma-H2AX foci, generally considered to mark DNA double-strand breaks (DSBs), were on chromosome arms or at chromosome ends. We found that while the numbers of non-telomeric DSBs were remarkably similar in these cultures, considerable variation was detected in the level of telomeric damage. The distinct heterogeneity in the numbers of gamma-H2AX foci in these tumor cell lines was found to be due to foci associated with uncapped telomeres, and the amount of total telomeric damage also appeared to inversely correlate with the telomerase activity present in these cells. These results indicate that damaged telomeres are the major factor accounting for the variability in the amount of DNA DSB damage in tumor cells. This characterization of DNA damage in tumor cells helps clarify the contribution of non-telomeric DSBs and damaged telomeres to major genomic alterations.
人类肿瘤和培养细胞中存在因端粒功能障碍、复制和转录错误、活性氧以及基因组不稳定导致的内源性DNA损伤水平升高。然而，端粒相关与端粒非依赖性内源性DNA损伤对这种损伤的贡献从未被研究过。在本研究中，我们通过观察通常被认为标记DNA双链断裂（DSB）的γ-H2AX焦点是在染色体臂上还是在染色体末端，来表征五种肿瘤细胞系中这两种类型DNA损伤的相对量。我们发现，虽然这些培养物中非端粒DSB的数量非常相似，但端粒损伤水平存在显著差异。这些肿瘤细胞系中γ-H2AX焦点数量的明显异质性被发现是由于与未加帽端粒相关的焦点，并且总端粒损伤量似乎也与这些细胞中存在的端粒酶活性呈负相关。这些结果表明，受损端粒是导致肿瘤细胞中DNA DSB损伤量变化的主要因素。对肿瘤细胞中DNA损伤的这种表征有助于阐明非端粒DSB和受损端粒对主要基因组改变的贡献。
