The transforming protein of avian reticuloendotheliosis virus is a soluble cytoplasmic protein which is associated with a protein kinase activity.
We have identified the product (p57v-rel) of the transforming gene, v-rel, of avian reticuloendotheliosis virus (REV-T) using antisera generated against nonoverlapping sequences representing the middle and carboxy-terminal regions of the v-rel protein expressed in Escherichia coli (N.K. Herzog and H.R. Bose, Jr., 1986, Proc. Natl. Acad. Sci. USA 83, 812-816). The amino-terminal region of the v-rel protein was also expressed in E. coli and used to generate antisera. The immunoglobulin-enriched fractions of these antisera were used to determine the subcellular location of p57v-rel in REV-T transformed lymphoid cells. Cells were fractionated into nuclear, mitochondrial, microsomal, and cytoplasmic fractions. The majority of p57v-rel was found in the cytoplasm. Examination of REV-T transformed lymphoid cells labeled with 32Pi revealed that the majority of the phosphorylated form of the v-rel protein was also found in the cytoplasm. Indirect immunofluorescence of REV-T transformed cells gave a diffuse cytoplasmic pattern indicating that p57v-rel was not associated with any discrete cellular organelle. The distribution of p57v-rel was similar in REV-T transformed lymphoid cells labeled with [35S]methionine for short and long periods of time, suggesting that p57v-rel is a soluble cytoplasmic protein throughout its lifetime. The v-rel protein was phosphorylated when immune complexes precipitated from transformed cells with the immunoglobulin fractions obtained from antisera against the amino-terminal, middle, and carboxy-terminal regions of v-rel were incubated with [gamma-32P]ATP and Mn2+. The phosphorylation of p57v-rel in the in vitro immune complex kinase assay was inhibited when the immunoglobulin-enriched fraction of these antisera was preincubated with the homologous v-rel fusion proteins. Preincubation with heterologous proteins did not block the phosphorylation of p57v-rel. These observations suggest that p57v-rel is associated with a protein kinase activity. Most of the kinase activity was found in the soluble cytoplasmic fraction of transformed cells. The transforming protein encoded by v-rel is a relatively stable protein with a half-life of approximately 7 to 8 hr in transformed lymphoid cells.
Walro
D S
DS
Department of Microbiology, University of Texas at Austin 78712.
Herzog
N K
NK
Zhang
J
J
Lim
M Y
MY
Bose
H R
HR
D002472:Cell Transformation, Viral; D003593:Cytoplasm / Q000378:metabolism; D007158:Immunologic Techniques; D008214:Lymphocytes / Q000382:microbiology; D008970:Molecular Weight; D009856:Oncogene Proteins, Viral / Q000502:physiology*; D009857:Oncogenes; D010750:Phosphoproteins / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D001356:Reticuloendotheliosis virus / Q000235:genetics*; D012190:Retroviridae / Q000235:genetics*; D012995:Solubility
D009856:Oncogene Proteins, Viral; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D011494:Protein Kinases