RAT MAF-RELATED FACTORS - THE SPECIFICITIES OF DNA-BINDING AND HETERODIMER FORMATION

maf is a family of genes encoding bZIP transcription factors. We isola ted two cellular maf-related cDNAs, maf-1 (mafB) and maf-2 (c-maf), fr om rat and determined the specificities of DNA binding and heterodimer formation. Although both Mafs strongly bind to MARE, the consensus Ma f recognition sequence (MARE, -TGCTGACTCAGCA-), originally identified by v-Maf protein Maf-1, recognizes a number of sequences containing on ly the first half of the MARE, -GCTGAC-. On the other hand, no such co nsensus short sequence could be determined for Maf-2. We determined th e specificities of heterodimer formation with all members of the Jun a nd Fos family. In contrast to v-Maf which forms heterodimers with all Jun and Fos proteins, Maf-1 heterodimerizes with all four Fos proteins , but not at all with the three Jun proteins. Maf-2 heterodimerizes wi th c-Fos. Me have also found that heterodimer formation of Maf-2 with c-Fos dramatically changes the specificity of DNA binding and trans-ac tivation activity from that of the Maf-2 homodimer. These results show that Maf-1 and Maf-2 have significantly different properties and they might have different target genes and functions, in spite of the simi larity of their bZip domain structure. (C) 1998 Academic Press.