Mapping of the functional domains of the v-rel oncogene

Previously, the v-rel oncogene was shown to code for a protein of 503 amino acids. The protein product of v-rel was identified as a 59 kDa protein (pp59v-rel), phosphorylated predominantly on serine residues. Although the signal required for the nuclear localization of pp59v-rel in chicken embryo fibroblasts was identified, the regions of v-rel important for transformation have not been mapped. In this study, 12 linker insertion mutants of v-rel were constructed and tested for transforming activity. Seven linker insertion mutants which mapped between amino acid residues 29 and 275 abolished transformation. The remaining 5 mutants which contained linker insertion mutations between amino acid residues 332 and 459 transformed at wild type levels. The results of this analysis localize the functional domains of the v-rel oncogene to the N-terminus. Earlier reports have shown that pp59v-rel resides in a high molecular weight complex with several other cellular proteins. The transforming mutants co-precipitated the same set of cellular proteins when immunoprecipitated with v-rel antiserum. This indicates that all transforming mutants retained the ability to bind within the reported complex.