Etiology of the translocation mediated by cruciform DNA

体质t(11；22)是人类中唯一已知的复发性非罗伯逊易位。T(11；22)的断裂点位于11q23和22q11的回文富含AT重复序列(PATRR)内。我提出，PATRR形成十字形结构，导致基因组不稳定，导致易位。在这项研究中，我分析了克隆的11号染色体PATRR的三级结构。通过双向琼脂糖凝胶电泳、核酸酶敏感性分析、凝胶迁移率改变分析和原子力显微镜观察，我证明了PATRR在体外形成了十字形结构(J Biol Chem，2004)。由于其潜在的二级结构，PATRR的序列分析很困难。我对PATRR的扩增、测序和克隆条件进行了优化，克服了这一困难，并成功地分析了PATRR的多态性(Hum Mutat，2005)。利用易位特异性聚合酶链式反应，我在正常健康人的精子样本中检测到了高频率的新基因t(11；22)。我还证明了PATRR的多态影响从头易位的频率(《科学》，2006)。这些观察结果支持了我关于回文介导的易位机制的假设。

Constitutional t(11;22) is the only known recurrent non-Robertsonian translocation in humans. The breakpoints of t(11;22) are located within palindromic AT-rich repeats (PATRRs) on 11q23 and 22q11. I proposed that the PATRR forms cruciform structure that induces genomic instability leading to the translocation. In this study, I analyzed the tertiary structure of the cloned PATRR of chromosome 11. I demonstrated that the PATRR formed cruciform structure in vitro using 2-dimensional agarose gel electrophoresis, nuclease sensitivity assay, electrophoresis mobility shift assay, and atomic force microscopy (J Biol Chem, 2004). The sequence analysis of the PATRR is difficult because of its potential secondary structure. I optimized the PCR, sequencing, and cloning condition to overcome the difficulty and analyzed polymorphism of the PATRR successfully (Hum Mutat, 2005). Using translocation-specific PCR, I detected de novo t(11;22) at high frequency in sperm samples obtained from normal healthy individuals. I also demonstrated that the polymorphism of the PATRR affects the frequency of de novo translocation (Science, 2006). These observations added support to my hypothesis for mechanism of palindrome-mediated translocation.