Localization of the v-rel protein in reticuloendotheliosis virus strain T-transformed lymphoid cells

The protein (p59/sup rel/) encoded by the transforming gene of reticuloendotheliosis virus strain T (REV-T) has been identified in REV-T-transformed avian lymphoid cells by using antisera raised against synthetic peptides whose sequences were derived from three nonoverlapping regions of v-rel. To obtain polyclonal antibodies directed against a larger number of p59/sup rel/ epitopes, a 262-amino acid segment was expressed in bacteria. Antisera raised against this fusion protein (v-Δ-rel) precipitated p59/sup rel/ from lysates of [35S]methionine-labeled REV-T-transformed cells, thus confirming previous results obtained with peptide antisera. The authors used this new antiserum to localize p59/sup rel/ in REV-T-transformed cells by subcellular fractionation using differential centrifugation and by indirect immune fluorescent staining. After fractionation and immune precipitation, the majority of p59/sup rel/ was found in the cytoplasmic fraction. Indirect immunofluorescence experiments also gave results consistent with the cytoplasmic localization of the v-rel protein in transformed lymphoid cells. In previous studies, it was shown that immune precipitates formed with one of the three p59/sup rel/ peptide antisera possessed in vitro protein kinase activity. Immune precipitates formed with the fusion protein antiserum also showed kinase activity in the in vitro assay. Most of this activity was found in the soluble cytoplasmic fraction, indicating that the kinase may be p59/sup rel/ or a protein closely associated with it