Studies Of Immunoglobulin Gene Rearrangement

在淋巴发育过程中，功能性免疫球蛋白和T细胞受体基因通过称为V（D）J重组的过程从基因片段组装，这对于产生免疫应答的多样性至关重要。在该反应的第一阶段，通过RAG 1/RAG 2蛋白复合物在靶位点（RSS）处产生特异性双链断裂。随后的步骤需要重新连接使用许多蛋白质因子，这些因子也用于修复X射线损伤。我们最近的工作集中在RAG蛋白上。我们表明，整个RAG 1/2大会开始重组所需的结合到一个单一的识别序列，和互补序列进入这个复杂的裸DNA。这种突触复合物的形成被迫通过这种途径;如果RAG 1/2在混合之前分别结合两个序列，则会受到抑制。该途径有助于确保正确的位点对用于重组。 已知RAG-DNA复合物能够将其识别序列转座到第二DNA中。我们现在发现了一种新的？反向换位？其中非特异性DNA被切割并随后用于攻击识别序列。尽管RAG 1/2仅与非特异性DNA弱结合，但RAG 1/2在细胞中的过量超过了识别序列，因此这种反应可能偶尔发生，这为淋巴肿瘤中存在的染色体易位提供了另一种可能的机制。

During lymphoid development, functional immunoglobulin and T cell receptor genes are assembled from gene segments by a process called V(D)J recombination, which is essential for generating the diversity of the immune response. In the first stage of this reaction, specific double-strand breaks are made at the target sites (RSS) by the RAG1/RAG2 protein complex. The later steps necessary for rejoining employ many protein factors that are also used for repair of X-ray damage. Our recent work has concentrated on the RAG proteins. We show that the whole RAG1/2 assembly necessary to start recombination binds to a single recognition sequence, and the complementary sequence enters this complex as naked DNA. Formation of this synaptic complex is forced to go by this route; it is inhibited if RAG1/2 binds the two sequences separately prior to mixing. This pathway helps to ensure that correct pairs of sites are used for recombination. A RAG-DNA complex is known to be capable of transposing its recognition sequences into a second DNA. We have now found a new kind of ?inverse transposition?, in which non-specific DNA is cleaved and subsequently used to attack a recognition sequence. Although non-specific DNA is bound only weakly by RAG1/2, it is in such excess in cells over the recognition sequences that this reaction may happen occasionally, providing another possible mechanism for chromosomal translocations present in lymphoid tumors.