v-maf, a viral oncogene that encodes a "leucine zipper" motif

We have molecularly cloned the provirus of the avian musculoaponeurotic fibrosarcoma virus AS42. Nucleotide sequence analysis of a biologically active clone of AS42 showed that this virus encodes a viral oncogene, maf. The deduced amino acid sequence of the v-maf gene product contains a "leucine zipper" motif similar to that found in a number of DNA binding proteins, including the gene products of the fos, jun, and myc oncogenes. However, unlike these oncogenes, the cellular maf gene was not transcriptionally activated by growth stimulation of cultured cells.