Features of the N-terminal non-core region of RAG1. The CND and ZDD structural domains are shown as blue boxes. The RING finger (residues 267-328) and zinc finger A (ZFA; residues 355-376) within the ZDD [46, 47] are indicated by brackets. As described previously , the RING finger in RAG1, labeled RING(+ext), contains an N-terminal extension that allows formation of the zinc binuclear cluster. Three motifs consisting of clusters of basic residues are shown as red bars. These basic motifs are referred to as BI, BII, and BIII, and consist of residues 141-146 (BI), residues 222-225 (BII), and 243-249 (BIII) .