title: Avian acute leukemia virus OK10 has an 8.2-kilobase genome and modified glycoprotein gp 78.
abstract: We have analyzed the structure of OK10-BM virus, an avian acute leukemia virus produced by a bone marrow-derived cell line of macrophage origin, and compared it with that of OK10 AV, an associated virus originally present in the OK10 virus stock. The RNAs of OK10-BM virus and OK10 AV had the same mobility in agarose gels, corresponding to 8.0 to 8.5 kilobases, a size considerably larger than that of the transforming component (5 to 6 kb) of most other avian acute leukemia viruses. Fingerprint analysis showed a close relationship between OK10-BM virus and OK10 AV RNAs. The polypeptide compositions of OK10-BM and OK10 AV viruses were similar except for the envelope glycoproteins. In analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the large envelope glycoprotein of OK10-BM virus migrated at M(r) = 78,000 (gp78), whereas OK10 AV had the characteristic 85,000-dalton glycoprotein (gp85) of nondefective avian leukemia viruses. gp78 was weakly labeled with methionine, glycine, proline, or mannose, suggesting that purified OK10-BM virus had reduced amounts of the modified envelope glycoprotein. In cell-free rabbit reticulocyte lysates, OK10-BM virion RNA directed the synthesis of a 200,000-dalton polypeptide (p200), a 180,000-dalton polypeptide (pr180), and a 76,000-dalton polypeptide (pr76), whereas OK10 AV RNA gave rise only to pr180 and pr76, suggesting that p200 may represent an OK10-BM-encoded transforming protein. No biochemical evidence for the presence of an associated helper virus was found in the OK10-BM virus population produced by the macrophage cell line. However, when OK10-BM virus was serially passaged in chicken embryo fibroblasts, a virus having structural properties similar to those of OK10 AV (OK10 AV-specific oligonucleotides and gp85) appeared after three passages. Moreover, nonproducer clones of transformed cells could be readily obtained in OK10-BM virus-infected quail cell cultures. It is thus likely that the bone marrow-derived macrophage cell line produces a transforming virus defective in its env gene and low amounts of an associated helper virus, which upon transfer to fibroblasts is preferentially replicated.
mesh_terms: D000818:Animals; D001354:Avian Leukosis Virus / Q000032:analysis / Q000235:genetics* / Q000254:growth & development; D001853:Bone Marrow; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002472:Cell Transformation, Viral; D002642:Chick Embryo; D005347:Fibroblasts; D005814:Genes, Viral; D006023:Glycoproteins / Q000032:analysis*; D009843:Oligoribonucleotides / Q000032:analysis; D014176:Protein Biosynthesis; D012367:RNA, Viral / Q000032:analysis*; D014764:Viral Proteins / Q000032:analysis*
chemical_list: D006023:Glycoproteins; D009843:Oligoribonucleotides; D012367:RNA, Viral; D014764:Viral Proteins