Mundy Cynthia L, Patenge Nadja, Matthews Adam G W, Oettinger Marjorie A
Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Mol Cell Biol. 2002 Jan;22(1):69-77. doi: 10.1128/MCB.22.1.69-77.2002.
Assembly of antigen receptor genes by V(D)J recombination requires the site-specific recognition of two distinct DNA elements differing in the length of the spacer DNA that separates two conserved recognition motifs. Under appropriate conditions, V(D)J cleavage by the purified RAG1/RAG2 recombinase is similarly restricted. Double-strand breakage occurs only when these proteins are bound to a pair of complementary signals in a synaptic complex. We examine here the binding of the RAG proteins to signal sequences and find that the full complement of proteins required for synapsis of two signals and coupled cleavage can assemble on a single signal. This complex, composed of a dimer of RAG2 and at least a trimer of RAG1, remains inactive for double-strand break formation until a second complementary signal is provided. Thus, binding of the second signal activates the complex, possibly by inducing a conformational change. If synaptic complexes are formed similarly in vivo, one signal of a recombining pair may be the preferred site for RAG1/RAG2 assembly.
通过V(D)J重组组装抗原受体基因需要位点特异性识别两个不同的DNA元件，这两个元件在分隔两个保守识别基序的间隔DNA长度上存在差异。在适当条件下，纯化的RAG1/RAG2重组酶对V(D)J的切割也有类似限制。只有当这些蛋白质在突触复合体中与一对互补信号结合时，才会发生双链断裂。我们在此研究RAG蛋白与信号序列的结合，发现两个信号突触形成和偶联切割所需的完整蛋白质补充可以组装在单个信号上。这种由RAG2二聚体和至少RAG1三聚体组成的复合体，在提供第二个互补信号之前，对于双链断裂形成仍无活性。因此，第二个信号的结合可能通过诱导构象变化来激活该复合体。如果在体内以类似方式形成突触复合体，重组对中的一个信号可能是RAG1/RAG2组装的首选位点。
