Discreet mutations from c-Rel to v-Rel alter kappaB DNA recognition, IkappaBalpha binding, and dimerization: implications for v-Rel oncogenicity.

The avian Rev-T retrovirus encodes the oncoprotein v-Rel, a member of the Rel/nuclear factor (NF)-kappaB transcription factor family. The aggressive oncogenic potential of v-Rel has arisen from multiple mutations within the coding sequence of the avian cellular protein c-Rel. In this study, using quantitative biochemical experiments, we have tested the role of a limited set of alterations between v-Rel and c-Rel located within the Rel homology region (RHR) of the family that might confer functional differences. Our results show that only a set of six mutations within the RHR of v-Rel are responsible for its ability to bind to a broad spectrum of kappaB-DNA that are normally regulated by distinct NF-kappaB dimers. We also observe that both v-Rel homodimer and p50/v-Rel heterodimer bind IkappaBalpha weakly compared to other cellular Rel/NF-kappaB dimers with transcription activation potential. We suggest that the ability of v-Rel homodimer to deregulate subunit-specific gene expression and its ability to evade IkappaB inhibition are crucial to its strong oncogenic potential.