The role of the carboxy terminus of v-Rel in transformation and activation of endogenous gene expression.

Proteins within the Rel/NF-kappa B transcription factor family can be divided into two functional domains, a homologous amino terminal region, the Rel Homology Domain, and a divergent carboxy terminal domain. The amino terminal sequences specify DNA binding, nuclear localization, and interaction with the I kappa B family of inhibitory proteins. The carboxy terminus of each protein functions as a transcriptional activation domain, however, precise definition of sequence requirements has been difficult. To further define these sequences, small 100 bp deletions were constructed throughout the carboxy terminus of v-Rel. Each resulting mutant was assayed for DNA binding, localization, protein complex formation, activation of endogenous gene expression and ability to transform bone marrow cells and fibroblasts. Surprisingly, deletion within the carboxy terminus had marginal effects on transforming potential. However, three separate regions were required for full activation of gene expression. Taken together, these results suggest that the carboxy terminus of v-Rel contains multiple sequences that participate in the activation of gene expression.