Identification of the R1 oncogene and its protein product from the rhadinovirus of rhesus monkeys

Rhesus monkey rhadinovirus (RRV) is a gamma-2 herpesvirus that is most clos ely related to the human Kaposi's sarcoma-associated herpesvirus (KSHV). We have identified a distinct open reading frame at the left end of RRV and d esignated it R1, The position of the R1 gene is equivalent to that of the s aimiri transforming protein (STP) of herpesvirus saimiri (HVS) and of K1 of KSHV, other members of the gamma-2 or rhadinovirus subgroup of herpesvirus es, The R1 sequence revealed an open reading frame encoding a product of 32 3 amino acids that was predicted to contain an extracellular domain, a tran smembrane domain, and a C-terminal cytoplasmic tail reflective of a type I membrane-bound protein. The predicted structural motifs of R1, including th e presence of immunoreceptor tyrosine-based activation motifs, resembled th ose in K1 of KSHV but were distinct from those of STP. R1 sequences from fo ur independent isolates from three different macaque species revealed 0.95 to 7.3% divergence over the 423 amino acids. Variation was located predomin antly within the predicted extracellular domain. The R1 protein migrated at 70 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and wa s extensively glycosylated. Tagged R1 protein was localized to the cytoplas mic and plasma membranes of transfected cells. Expression of the R1 gene in Rat-1 fibroblasts induced morphologic changes and focus formation, and inj ection of R1-expressing cells into nude mice induced the formation of multi focal tumors. A recombinant herpesvirus in which the STP oncogene of HVS wa s replaced by RI immortalized T lymphocytes to interleukin-2-independent gr owth. These results indicate that R1 is an oncogene of RRV.