DIFFERENCES IN KAPPA-B DNA-BINDING PROPERTIES OF V-REL AND C-REL ARE THE RESULT OF ONCOGENIC MUTATIONS IN 3 DISTINCT FUNCTIONAL REGIONS OF THE REL PROTEIN

The oncogene v-rel of Reticuloendotheliosis virus, strain T, is derive d from an avian c-rel proto-oncogene, c-rel encodes a member of the Re l/NF-kappa B family of transcription factors, The highly oncogenic v-R el differs from c-Rel which has low transforming potential by the acqu isition of numerous mutations, In this manuscript, we demonstrate that the oncogenic mutations in v-Rel directly alter the ability of this p rotein to bind to DNA, Electrophoretic mobility shift analysis with Re l proteins synthesized in vitro as well as isolated from nuclei of Rel expressing cells showed that three mutation clusters, present in the N-terminus, the center and the C-terminus of v-Rel, altered three diff erent aspects of DNA binding, In contrast, the oncogenic C-terminal de letion of 118 amino acids present in v-Rel had almost no influence on its DNA binding. The N-terminal mutation cluster altered the kappa B D NA-binding specificity of the v-Rel oncoprotein relative to c-Rel. The mutation Met-20-->Thr was found to be principally responsible for thi s alteration, The second mutation cluster was responsible for increase d binding of v-Rel to all the KB sites examined presumably because it stabilized v-Rel homodimers, This alteration in DNA binding was mapped to the group of two mutations within the cluster, In contrast, the th ird mutation cluster in the C-terminus of v-Rel destabilized the bindi ng of v-Rel to all of the kappa B sites examined, This is the first in dication that regions outside the Rel Homology Region can participate in the control of binding of the c-Rel protein to DNA, The three mutat ion clusters examined contributed to the tumorigenic potential of v-Re l with the relative strength decreasing with their position from the N -terminus to the C-terminus, These results suggest that the oncogenic mutations in v-Rel cooperate and enable v-Rel to form nuclear complexe s with aberrant DNA-binding properties that may directly alter gene ex pression and DNA replication resulting in the transformation of the ce ll.