Oncogenic transformation by vrel requires an amino-terminal activation domain

The mechanism by which the products of the v-rel oncogene, the corresponding c-rel proto-oncogene, and the related dorsal gene of Drosophila melanogaster exert their effects is not clear. Here we show that the v-rel, chicken c-rel, and dorsal proteins activated gene expression when fused to LexA sequences and bound to DNA upstream of target genes in Saccharomyces cerevisiae. We have defined two distinct activation regions in the c-rel protein. Region I, located in the amino-terminal half of rel and dorsal proteins, contains no stretches of glutamines, prolines, or acidic amino acids and therefore may be a novel activation domain. Lesions in the v-rel protein that diminished or abolished oncogenic transformation of avian spleen cells correspondingly affected transcription activation by region I. Region II, located in the carboxy terminus of the c-rel protein, is highly acidic. Region II is not present in the v-rel protein or in a transforming mutant derivative of the c-rel protein. Our results show that the oncogenicity of Rel proteins requires activation region I and suggest that the biological function of rel and dorsal proteins depends on transcription activation by this region.