The genomic landscape neighboring large deletions including the hypoxanthine-guanine phosphoribosyl transferase (HPRT) locus on human X chromosome in 6-thioguanine-resistant mutants originating from immortalized human fibroblast cells exposed to X rays was characterized by real-time quantitative PCR (qPCR)-based analyses. Among the 13 mutant clones with large deletions extending over several Mb, including the HPRT locus, revealed by 10 conventional sequence-tagged site (STS) markers, three clones bearing the largest deletions were selected for further qPCR analysis using another 21 STS markers and 15 newly designed PCR primer pairs. The results indicated that the major deletions were in very specific regions between the 130-Mb and 140-Mb positions containing the HPRT locus on the X chromosome and, contrary to our initial expectations, additional minor deletions were distributed in a patchwork pattern. These findings strongly indicate that the complex deletion patterns in the affected chromosome are related to the radiation track structure with spatially heterogeneous energy deposition and the specific structure of the chromatin-nuclear membrane complex. The uncovered complex deletion patterns are in agreement with the idea of complex chromatin damage, which is frequently associated with carcinogenesis.

在源自暴露于 X 射线的永生化人成纤维细胞的 6-硫鸟嘌呤抗性突变体中，邻近大缺失的基因组景观包括人 X 染色体上的次黄嘌呤-鸟嘌呤磷酸核糖转移酶 ( HPRT ) 基因座，其特征在于实时定量 PCR (qPCR)-基于分析。在10 个常规序列标记位点 (STS) 标记显示的 13 个包含HPRT基因座在内的大缺失突变克隆中，选择了三个缺失最大的克隆，使用另外 21 个 STS 标记和 15新设计的 PCR 引物对。结果表明，主要缺失位于包含HPRT的 130-Mb 和 140-Mb 位置之间的非常特定的区域X 染色体上的基因座，并且与我们最初的预期相反，额外的小缺失以拼凑的方式分布。这些发现有力地表明，受影响染色体中复杂的缺失模式与具有空间异质能量沉积的辐射轨迹结构和染色质-核膜复合物的特定结构有关。发现的复杂缺失模式与复杂染色质损伤的想法一致，后者通常与致癌作用有关。