A novel cell transformation with DNA-containing cytoplasmic yaba tumor poxvirus

Abstract

Monkey kidney cells were morphologically transformed in vitro with uv-irradiated Yaba tumor poxvirus. Cell lines established were shown to be virus nonproducers and exhibited biological characteristics typical of transformed cells. These characteristics included increased saturation density, reduced serum requirements for growth, and ability to grow in soft agar. The morphological alterations of transformed cells were similar to Yaba virus-induced tumor cells and were characterized by loss of contact inhibition, multinucleated cells, and cytoplasmic lipid droplets. Southern blot hybridization revealed that sequences homologous to low-molecular-weight viral DNA (5.1, 4.8, 3.9 kbp) were present in the transformed cells. Yaba virus-specific antigens detected by immunofluorescence assays were found to be in the cytoplasm of transformed cells. Four virus-specific proteins, with molecular weights of 160,000, 140,000 107,000, and 74,000 daltons, were detected in transformed cells immunoprecipitated with sera from tumor-bearing monkeys. These results indicate that DNA-containing Yaba tumor virus, which replicates exclusively in the cytoplasm, is capable of inducing cell transformation in vitro.