HETEROLOGOUS C-TERMINAL SEQUENCES DISRUPT TRANSCRIPTIONAL ACTIVATION AND ONCOGENESIS BY P59(V-REL)

Members of the NF-kappaB/rel family of transcription factors are regulated through a trans association with members of a family of inhibitor proteins, collectively known as IkappaB proteins, that contain five to eight copies of a 33-amino-acid repeat sequence (ankyrin repeat). Certain NF-kappaB/rel proteins are also regulated by cis-acting ankyrin repeat-containing domains. The C terminus of p105NF-kappaB, the precursor of the 50-kDa subunit of NF-kappaB, contains a series of ankyrin repeats; proteolytic removal of this ankyrin domain is necessary for the manifestation of sequence-specific DNA binding and nuclear translocation of the N-terminal product. To investigate the structural requirements important for regulation of different NF-kappaB/rel family members by polypeptides containing ankyrin repeat domains, we have constructed a p59v-rel:p105NF-kappaB chimeric protein (p110v-rel-ank). The presence of C-terminal p105NF-kappaB-derived sequences in p110v-rel-ank inhibited nuclear translocation, sequence-specific DNA binding, pp40IkappaB-alpha association, and oncogenic transformation. Sequential truncation of the C-terminal ankyrin domain of p110v-rel-ank resulted in the restoration of nuclear translocation, DNA binding, and pp40IkappaB-alpha association but did not restore the oncogenic properties of p59v-rel. The presence of 67 C-terminal p105NF-kappaB-derived amino acids was sufficient to inhibit both transcriptional activation and oncogenic transformation by p59v-rel. These results support a model in which activation of gene expression by p59v-rel is required for its ability to induce oncogenic transformation.