Laboratorio de Citogenética y Mutagénesis, Instituto Multidisciplinario de Biología Celular (IMBICE, CCT-CONICET La Plata - CICPBA), C.C. 403, 1900 La Plata, Argentina.
Laboratorio de Citogenética y Mutagénesis, Instituto Multidisciplinario de Biología Celular (IMBICE, CCT-CONICET La Plata - CICPBA), C.C. 403, 1900 La Plata, Argentina.
Mutat Res. 2012 Aug 30;747(1):46-52. doi: 10.1016/j.mrgentox.2012.03.011. Epub 2012 Apr 4.
We analyzed the induction of chromosomal aberrations in Chinese hamster ovary (CHO) cells exposed to the radiomimetic compound streptonigrin (SN), in order to determine whether interstitial telomeric sequences (ITSs) are involved in the long-term clastogenic effect of this antibiotic. CHO cells were treated with a single concentration of SN (100ng/ml), and the frequency of unstable chromosomal aberrations was determined at three times after treatment (18h, and 6 and 15 days) by using PNA-FISH with a pan-telomeric probe. Cytogenetic analysis revealed a higher frequency of aberrations at 18h and 6 days after treatment in SN-exposed cultures vs. untreated cultures. The percentage of damaged cells and the yield of SN-induced aberrations at 6 days after treatment increased on average twofold compared with the ones at 18h after treatment. Moreover, a significant decrease in the frequency of aberrations was observed in SN-exposed cells at 15 days after treatment, resulting in a frequency of aberrations significantly lower than the frequency of aberrations observed in the corresponding control cultures. These data indicate that SN induces delayed chromosomal instability in CHO cells, and that the in vitro clastogenic effect of this compound persists for at least 6 days but less than 15 days after treatment. In addition, we found that SN induces delayed ITSs instability, cytogenetically detectable as additional FISH signals and centromeric breaks involving dissociation of the telomeric signal 6 days after treatment. We propose that the delayed effect of SN on ITSs results from breakage of heterochromatic centromeric ITSs blocks and further insertion of these sequences at the sites of mono- or isochromatid breaks occurring at G2 or G1-S phases of the cell cycle, respectively, since most of the additional FISH signals were present as single or double dots, and located at interstitial sites of the involved chromosomes.
我们分析了中国仓鼠卵巢（CHO）细胞暴露于类放射化合物链黑菌素（SN）后染色体畸变的诱导，以确定端粒间序列（ITSs）是否参与该抗生素的长期断裂基因效应。CHO 细胞用单一浓度的 SN（100ng/ml）处理，并在处理后 3 次（18h 和 6 天和 15 天）用 PNA-FISH 用泛端粒探针测定不稳定染色体畸变的频率。细胞遗传学分析显示，SN 暴露培养物在处理后 18h 和 6 天的畸变频率高于未处理培养物。与处理后 18h 相比，处理后 6 天的受损细胞百分比和 SN 诱导的畸变产量平均增加了两倍。此外，在处理后 15 天，SN 暴露细胞中的畸变频率显著降低，导致畸变频率显著低于相应对照培养物中的畸变频率。这些数据表明，SN 在 CHO 细胞中诱导延迟的染色体不稳定性，并且该化合物的体外断裂基因效应在处理后至少持续 6 天但少于 15 天。此外，我们发现 SN 诱导延迟的 ITSs 不稳定性，细胞遗传学上可检测为额外的 FISH 信号和涉及端粒信号分离的着丝粒断裂，在处理后 6 天。我们提出，SN 对 ITSs 的延迟效应是由于异染色质着丝粒 ITSs 块的断裂以及进一步将这些序列插入在细胞周期的 G2 或 G1-S 期发生的单或等臂断裂部位，因为大多数额外的 FISH 信号呈现为单个或双点，并且位于涉及染色体的间质部位。
