Molecular cloning of a translocation breakpoint hotspot in 22q11
Molecular cloning of a translocation breakpoint hotspot in 22q11
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DOI：
10.1101/gr.5769507
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发表时间：
2007-04-01
期刊：
影响因子：
7
通讯作者：
Emanuel, Beverly S.
中科院分区：
文献类型：
--
作者：
Kurahashi, Hiroki;Inagaki, Hidehito;Emanuel, Beverly S.
有充分的证据表明，22q11包含人类基因组中最容易重排的位点之一，许多结构易位的断点聚集在这里。这个断裂敏感区域位于人类基因组计划中剩余的不可克隆的间隙之一，暗示了一个难以克隆的特定序列。在这项研究中，我们克隆了该缺口的一部分，并鉴定了一个新的595 bp的回文AT-rich repeat （PATRR）。到目前为止，我们已经确定了三个易位相关的PATRRs。它们的共同特点是：(1)它们是富含at的近乎完美的回文，长度为几百个碱基对；(2)在patr两端均存在非at -rich区域；(3)它们在patr的一侧显示了另一个附近的at富区。所有这些特征都暗示了DNA二级结构的可能性。无亲缘关系个体的序列分析显示没有主要的大小多态性，但显示个体之间的小核苷酸多态性以及近端和远端臂之间的顺式多态性。各种易位的断点分析表明，双链断裂（DSB）发生在回文的中心，通常伴有中心的小对称缺失。在配对染色体之间，断点只共享少量相同的核苷酸。综上所述，这些特征表明dsb是通过非同源端连接或单链退火修复的，而不是同源重组途径。所有这些结果都支持先前提出的一个范式，即不寻常的DNA二级结构在回文介导易位发生的机制中起作用。
It has been well documented that 22q11 contains one of the most rearrangement-prone sites in the human genome, where the breakpoints of a number of constitutional translocations cluster. This breakage-sensitive region is located within one of the remaining unclonable gaps from the human genome project, suggestive of a specific sequence recalcitrant to cloning. In this study, we cloned a part of this gap and identified a novel 595-bp palindromic AT-rich repeat (PATRR). To date we have identified three translocation-associated PATRRs. They have common characteristics: (1) they are AT-rich nearly perfect palindromes, which are several hundred base pairs in length; (2) they possess non-AT-rich regions at both ends of the PATRR; (3) they display another nearby AT-rich region on one side of the PATRR. All of these features imply a potential for DNA secondary structure. Sequence analysis of unrelated individuals indicates no major size polymorphism, but shows minor nucleotide polymorphisms among individuals and cis-morphisms between the proximal and distal arms. Breakpoint analysis of various translocations indicates that double-strand-breakage (DSB) occurs at the center of the palindrome, often accompanied by a small symmetric deletion at the center. The breakpoints share only a small number of identical nucleotides between partner chromosomes. Taken together, these features imply that the DSBs are repaired through nonhomologous end joining or single-strand annealing rather than a homologous recombination pathway. All of these results support a previously proposed paradigm that unusual DNA secondary structure plays a role in the mechanism by which palindrome-mediated translocations occur.