THE DNA-BINDING DOMAINS OF THE YEAST GAL4 AND HUMAN C-JUN TRANSCRIPTION FACTORS INTERACT THROUGH THE ZINC-FINGER AND BZIP MOTIFS

Different Gal4 fusion proteins, expressing unrelated transcription act ivator domains, were found to activate transcription from promoters co ntaining dimerized AP1 DNA binding sites, Transactivation was dependen t on the first 74 amino acids of Gal4, A direct Interaction between Ga l4 and c-Jun was demonstrated using a GSTGal4 fusion protein and in vi tro translated human c-Jun. The interaction required the zinc finger c ontaining DNA binding domain of Gal4 and the basic-leucine zipper regi on of c-Jun, These results demonstrated that the specificity of Gal4 f usion proteins in transient transfection experiments in mammalian cell s is not restricted to reporters containing Gal4 binding sites, but al so includes promoters containing AP1 binding sites, Furthermore, the G al4 fusion proteins also activated transcription from a pUC18 vector f ragment containing several putative API binding sites, Finally, our re sults indicate that Gal4 activator proteins binding to Gal4 binding si tes and to DNA bound AP1 factors can co-operatively activate transcrip tion.