Kaposi's sarcoma-associated herpesvirus (human herpesvirus-8) ORF54 encodes a functional dUTPase expressed in the lytic replication cycle.

The complete ORF54 of the Kaposi's sarcoma-associated herpesvirus (KSHV) (human herpesvirus-8; HHV-8) was cloned and expressed in E. coli. The results show that KSHV/HHV-8 ORF54 encodes a functional dUTPase which specifically hydrolyses dUTP to dUMP. Monoclonal antibodies against the HHV-8 dUTPase detected a protein with the expected molecular mass of 35 kDa in HHV-8-infected BCBL-1 cells. Induction of the lytic replication cycle of HHV-8 by treatment of BCBL-1 cells with the phorbol ester TPA resulted in an increased expression of the protein which was not inhibited by phosphonoacetic acid, indicating that the protein is expressed early in the lytic replication cycle. Moreover, the sporadic expression of the HHV-8 dUTPase in tissue sections of Kaposi's sarcoma was detected by immunohistochemistry.