Cooperative binding of c-Myb and Pax-5 activates theRAG-2 promoter in immature B cells

Abstract

Abstract The recombination activating gene-1 (RAG-1) andRAG-2 are expressed specifically in immature lymphoid cells undergoing the recombination of antigen receptor genes. The regulation of murine RAG-2 promoter was studied and it was revealed that the −41/−17 RAG-2 promoter region, which is conserved between humans and mice, was indispensable for theRAG-2 promoter activity in B-cell lines. The region contained 2 cis elements that bound c-Myb and Pax-5. Mutation in the c-Myb–binding site in the promoter reduced the promoter activity in B-cell lines. Cooperative activation of theRAG-2 promoter was seen by a combination of c-Myb and Pax-5 in a human embryonic kidney cell line (293T), via their synergistic DNA-binding. Deletion experiments showed that the C-terminus of c-Myb was responsible for their interaction. Furthermore, the dominant-negative c-Myb mutant suppressed the activation of theRAG-2 promoter in a pre–B-cell line as well as in 293T cells. These results suggest that cooperative binding of c-Myb and Pax-5 to the RAG-2 promoter is one of the mechanisms to direct the restricted expression of the RAG-2 in immature B cells.