Recombination activating gene-1 (RAG-1) and RAG-2 are expressed specifically in lymphocytes undergoing the antigen receptor gene rearrangement during the lymphocyte development. Our previous study showed that the -41 to -17 nucleotides (nt) 5'-up-stream region of mouse RAG-2 were pre-requisite for the core promoter activity and that Pax-5/c-Myb/LEF-1 protein-protein complex was responsible for its activity in immature B cells. In this study, we show that the -65/-42 sequence, the non-conserved sequence between human and mouse RAG-2 promoter, is necessary for the full promoter activity for mouse RAG-2. Electrophoresis mobility shift assay revealed that Myc-associated zinc finger protein (MAZ) as well as SPI/3 binds a GA box in this region. Using chromatin immunoprecipitation, we show that MAZ binds the RAG-2 promoter region in pre-B cells. Furthermore, we show that MAZ synergistically activates the murine RAG-2 promoter with Pax-5/c-Myb/LEF-1 complex. These results first demonstrate that MAZ participates in activation of mouse RAG-2 promoter. (C) 2004 Elsevier Inc. All rights reserved.