Petersen S, Saretzki G, von Zglinicki T
Institute of Pathology, Charité, Humboldt-University Berlin, Germany.
Exp Cell Res. 1998 Feb 25;239(1):152-60. doi: 10.1006/excr.1997.3893.
We have demonstrated recently that chronic hyperoxic treatment accelerates the rate of aging of fibroblasts and the rate of telomere shortening in parallel. It was hypothesized that accelerated telomere shortening is due to preferential accumulation of oxidative damage in telomeres. To test this hypothesis, we measured the accumulation of sites sensitive to S1 nuclease treatment in telomeres, in minisatellites, and in the bulk of the genome of fibroblasts under different models of oxidative stress as well as after treatment with the alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine. A comparison with qualitative data obtained by alkaline electrophoresis reveals that the sites transferred to double-strand breaks by treatment with low concentrations of S1 nuclease are, in fact, single-stranded regions in the DNA. These regions may resemble single-stranded overhangs, gaps, or conventional single-strand breaks. The frequency of single-stranded regions is significantly higher in telomeres than in minisatellites or in the bulk of the genome under all conditions tested. Those regions induced in minisatellites or in the overall genome by a bolus dose of hydrogen peroxide are completely repaired within 24 h. On the other hand, 50 +/- 12% of H2O2-induced single-stranded regions remain unrepaired for at least 19 days in telomeres of human fibroblasts, leading to a significant increase of the telomeric steady-state level of these lesions. This preferential accumulation might significantly contribute to telomere shortening.
我们最近证明，慢性高氧治疗会加速成纤维细胞的衰老速度，并同时加速端粒缩短的速度。据推测，端粒缩短加速是由于端粒中氧化损伤的优先积累。为了验证这一假设，我们测量了在不同氧化应激模型下以及在用烷基化剂N-甲基-N'-硝基-N-亚硝基胍处理后，成纤维细胞端粒、小卫星以及基因组主体中对S1核酸酶处理敏感的位点的积累情况。与碱性电泳获得的定性数据比较显示，用低浓度S1核酸酶处理后转化为双链断裂的位点实际上是DNA中的单链区域。这些区域可能类似于单链悬端、缺口或传统的单链断裂。在所有测试条件下，端粒中单链区域的频率明显高于小卫星或基因组主体中的频率。小卫星或整个基因组中由一次大剂量过氧化氢诱导产生的那些区域在24小时内完全修复。另一方面，在人成纤维细胞的端粒中，50±12%的过氧化氢诱导的单链区域至少19天未修复，导致这些损伤的端粒稳态水平显著增加。这种优先积累可能对端粒缩短有显著贡献。
