Figure 1.

Schematic focusing on the initial steps of V(D)J recombination. (A) The RAG complex composed of RAG1 (purple) and RAG2 (green) binds to the 12- and 23RSSs (dark purple and orange triangles, respectively) neighboring gene segments (shown as red and yellow boxes on the DNA), (B) forming the paired complex (PC). At any point when it is bound to an RSS, RAG can introduce a nick in the DNA between the heptamer and gene segment (shown with the magnified 12RSS) and must do so to both sites before (C) it cleaves the DNA to expose the gene segments. As indicated by the magnified gene segment end, the exposed DNA strands of the gene segment are connected to form a DNA hairpin. (D) Additional proteins join these segments together. In this work, the stages subsequent to DNA cleavage are not monitored.