Synergy of PEBP2/CBF with mi transcription factor (MITF) for transactivation of mouse mast cell protease 6 gene

The mi locus encodes a member of the basic-helix-loop-helix-leucine zipper (bHLH-Zip) protein family of transcription factors (hereafter called MITF), Although the bHLH-Zip family transcription factors generally recognize and bind CANNTG motifs, the expression of mouse mast cell protease 6 (MMCP-6) gene is regulated by MITF through the (G) under bar ACCTG motif in the prom oter region. The GACC<(TG)under bar> motif was partly overlapped the <(TG)u nder bar>TGGTC sequence, which was bound by polyomavirus enhancer binding p rotein 2 (PEBP2), In the present study, the effect of PEBP2 on the expressi on of MMCP-6 gene was examined, PEBP2 that is composed of alpha and beta su bunits was expressed by mast cell Lines and cultured mast cells derived fro m spleen, The overexpression of dominant negative PEBP2 cDNA reduced the ex pression of MMCP-6. Moreover, the simultaneous transfection of the plasmid containing MITF cDNA and the plasmid containing PEBP2 cDNA increased the MM CP-6 promoter activity, For the synergistic action of PEBP2 and MITF, the i ntact GACC<(TG)under bar> and <(TG)under bar>TGGTC motifs were prerequisite . The PEBP2 alpha B1 mutant which lacked the region downstream from the Run t domain did not bind MITF and lost the synergistic function. These results indicated that PEBP2 and MITF synergistically transactivated the MMCP-6 ge ne and that the region downstream from the Runt domain of PEBP2 alpha B1 wa s essential for the physical and functional interactions with MITF.