Characterization of the herpesvirus saimiri ORF73 gene product

The herpesvirus saimiri (HVS) gene product encoded by ORF73 shares a limite d homology with the ORF73 encoded protein of Kaposi's sarcoma-associated he rpesvirus (KSHV), It has recently been shown that the KSHV ORF73 protein is expressed during a latent infection and co-localizes with host cell chromo somes, suggesting that it plays a role in episomal maintenance by tethering viral genomes to host cell chromosomes. At present the role of the HVS ORF 73 gene product is unknown. However, the expression of HVS ORF73 in a stabl y transduced human carcinoma cell line, where the HVS genome persists as a non-integrated circular episome, has recently been shown. In this report, t he characterization of the HVS ORF73 protein and the mapping of its functio nal domains are described. The results suggest that the HVS ORF73 gene enco des a 64 kDa nuclear protein. Moreover, the amino terminus contains two fun ctional nuclear localization signals, whereas the carboxy terminus is requi red for the distinctive speckled nuclear distribution pattern as observed w ith both the HVS and KSHV ORF73 proteins.