Herpesvirus saimiri encodes homologues of G protein-coupled receptors and cyclins

HERPESVIRUS saimiri (HVS) is a T-lymphotropic gammaherpes-virus which establishes asymptomatic infections in its natural host the squirrel monkey (Saimiri sciureus), but which causes fatal lymphoproliferative diseases in other New World primates¹. Sequencing studies show HVS is closely related to the human B-lymphotropic gammaherpesvirus Epstein-Barr virus (EBV)^2-4. However, despite the general collinearity between the genomes of HVS and EBV, HVS contains genes not found in EBV or in the genomes of any of the other sequenced herpesviruses^5-8. We have identified two genes, occurring in a region of divergence between HVS and EBV, that have cellular homologues. One of these, ECRF3, is homologous to the genes encoding the human cytomegalovirus (HCMV) and cellular G protein-coupled receptor family of proteins⁹. The other HVS gene, ECLF2, is homologous to the genes encoding cellular cyclins and to our knowledge is the first reported example of a viral cyclin. The presence of G protein-coupled receptor and cyclin homologues in HVS suggests that these genes may be important in the regulation of viral and cellular processes during productive and/or latent infection of host cells, and in particular may be of relevance in the transformation and rapid proliferation of T cells during HVS infections of hosts susceptible to HVS-induced lymphoproliferative diseases.