STUDIES OF IMMUNOGLOBULIN GENE REARRANGEMENT

组装功能的V(D)J复合过程 淋巴细胞中的免疫球蛋白和T细胞受体基因 对产生免疫反应的多样性至关重要。这个 现在已知反应分两个阶段发生。在第一阶段， 特定的双链断裂发生在目标位置。两端 在这些断裂处的编码DNA序列总是连接在一起 他们自己就是DNA发夹。基于细胞实验，这一点 已知有一种不寻常的切割利用RAG1的产物 和RAG2基因，但尚不清楚它们是如何发挥作用的。后者 重组的各个阶段不那么具体；最终结合的产物 都是使用了许多也参与修复的因素 辐射损伤。我们现在复制了第一个切割反应 在仅需要纯化的RAG-1的生化定义的反应中 和RAG-2蛋白。包含识别信号的DNA片段 将序列(RSS)切割成发夹编码端和钝化信号 结束，就像在活体中一样。此外，在要求更高的反应中 条件，卵裂需要一对不同类型的RSS 它们是体内重组所必需的。因此，RAG蛋白 仅包含V(D)J的特异性的所有信息 重组。我们还发现，发夹是由一种 化学反应与转位重组非常相似。一个 V(D)J重组与转座的进化关系 元素，我们的结果提供了 到目前为止支持这一想法的最强劲的数据。

The V(D)J recombination process that assembles functional immunoglobulin and T cell receptor genes in lymphoid cells is essential for generating the diversity of the immune response. The reaction is now known to occur in two stages. In the first stage, specific double-strand breaks are made at the target sites. The ends of the coding DNA sequence at these breaks are always joined back on themselves as DNA hairpins. Based on cellular experiments, this unusual type of cleavage was known to utilize the products of the RAG1 and RAG2 genes, but it was not clear how they functioned. The later stages of recombination are less specific; the final joined products are made with the use of many factors also involved in the repair of radiation damage. We have now reproduced the first cleavage reaction in a biochemically defined reaction requiring only the purified RAG-1 and RAG-2 proteins. A DNA fragment containing the recognition signal sequence (RSS) is cut to make a hairpin coding end and a blunt signal end, just as in vivo. Furthermore, in more demanding reaction conditions, cleavage requires a pair of RSSs of the different types that are needed for recombination in vivo. Thus the RAG proteins alone contain all the information for the specificity of V(D)J recombination. We have also found that the hairpins are made in a reaction very similar chemically to transpositional recombination. An evolutionary relation between V(D)J recombination and transposable elements had previously been suggested, and our results provide the strongest data so far in support of this idea.