MAFA, A NOVEL MEMBER OF THE MAF PROTOONCOGENE FAMILY, DISPLAYS DEVELOPMENTAL REGULATION AND MITOGENIC CAPACITY IN AVIAN NEURORETINA CELLS

Transcription factors of the Maf proto-oncogene family have been shown to participate in the regulation of several differentiation specific genes. We previously reported that a member(s) of this family is invol ved in the regulation of the neuroretina specific gene, QR1, through a promoter region, designated the A box, that is closely related to the Maf recognition element (MARE). We undertook an identification of Maf family genes expressed in the quail neuroretina (QNR) and we report t he isolation of mafA, a gene encoding a novel member of the large Maf proteins subgroup. Expression of this gene is developmentally regulate d in the neuroretina, MafA is able to bind to MARE sequence and to het erodimerize with v-Maf, MafB, Jun and Fos, but not with the small MafF and MafK proteins. Accordingly, it is able to transactivate the QR1 p romoter A box. We also show that increased expression of mafA induces sustained proliferation of postmitotic QNR cells.