Moore Stephen R, Papworth David, Grosovsky Andrew J
Environmental Toxicology Graduate Program, Department of Cell Biology and Neuroscience, University of California, Riverside, CA, USA.
Mutat Res. 2006 Aug 30;600(1-2):113-24. doi: 10.1016/j.mrfmmm.2006.03.006. Epub 2006 May 23.
Genomic instability is observed in tumors and in a large fraction of the progeny surviving irradiation. One of the best-characterized phenotypic manifestations of genomic instability is delayed chromosome aberrations. Our working hypothesis for the current study was that if genomic instability is in part attributable to cis mechanisms, we should observe a non-random distribution of chromosomes or sites involved in instability-associated rearrangements, regardless of radiation quality, dose, or trans factor expression. We report here the karyotypic examination of 296 instability-associated chromosomal rearrangement breaksites (IACRB) from 118 unstable TK6 human B lymphoblast, and isogenic derivative, clones. When we tested whether IACRB were distributed across the chromosomes based on target size, a significant non-random distribution was evident (p<0.00001), and three IACRB hotspots (chromosomes 11, 12, and 22) and one IACRB coldspot (chromosome 2) were identified. Statistical analysis at the chromosomal band-level identified four IACRB hotspots accounting for 20% of all instability-associated breaks, two of which account for over 14% of all IACRB. Further, analysis of independent clones provided evidence within 14 individual clones of IACRB clustering at the chromosomal band level, suggesting a predisposition for further breaks after an initial break at some chromosomal bands. All of these events, independently, or when taken together, were highly unlikely to have occurred by chance (p<0.000001). These IACRB band-level cluster hotspots were observed independent of radiation quality, dose, or cellular p53 status. The non-random distribution of instability-associated chromosomal rearrangements described here significantly differs from the distribution that was observed in a first-division post-irradiation metaphase analysis (p=0.0004). Taken together, these results suggest that genomic instability may be in part driven by chromosomal cis mechanisms.
在肿瘤以及大部分受辐射后存活的子代中都观察到了基因组不稳定现象。基因组不稳定最典型的表型表现之一是延迟染色体畸变。我们当前研究的工作假设是，如果基因组不稳定部分归因于顺式机制，那么无论辐射质量、剂量或反式因子表达如何，我们都应该观察到参与不稳定相关重排的染色体或位点的非随机分布。我们在此报告了对来自118个不稳定的TK6人B淋巴母细胞及其同基因衍生克隆的296个不稳定相关染色体重排断裂位点（IACRB）的核型分析。当我们基于目标大小测试IACRB是否分布在染色体上时，明显存在显著的非随机分布（p<0.00001），并确定了三个IACRB热点（11号、12号和22号染色体）和一个IACRB冷点（2号染色体）。在染色体带水平的统计分析确定了四个IACRB热点，占所有不稳定相关断裂的20%，其中两个占所有IACRB的14%以上。此外，对独立克隆的分析提供了证据，表明在14个单独的克隆中IACRB在染色体带水平上聚集，这表明在某些染色体带发生初始断裂后更容易发生进一步断裂。所有这些事件，无论是单独发生还是综合起来，都极不可能是偶然发生的（p<0.000001）。这些IACRB带水平的簇热点的观察与辐射质量、剂量或细胞p53状态无关。此处描述的不稳定相关染色体重排的非随机分布与在辐照后第一次分裂中期分析中观察到的分布有显著差异（p=0.0004）。综上所述，这些结果表明基因组不稳定可能部分由染色体顺式机制驱动。
