HUMAN CYTOMEGALOVIRUS UL97 KINASE CONFERS GANCICLOVIR SUSCEPTIBILITY TO RECOMBINANT VACCINIA VIRUS

We analyzed whether the phosphotransferase encoded by the UL97 open re ading frame of human cytomegalovirus (HCMV) alone is sufficient to con fer ganciclovir (GCV) susceptibility to a foreign virus. Two vaccinia virus recombinants (T1 and A5) containing the UL97 open reading frames from a GCV-sensitive HCMV and from a GCV-resistant strain were constr ucted. T1 exhibited a GCV-sensitive phenotype in plaque reduction assa ys, whereas A5 did not. Moreover, T1-infected cell cultures showed a s trongly increased incorporation of [C-14]GCV triphosphate into macromo lecular DNA, compared with recombinant A5 or vaccinia virus controls, which could be inhibited by the addition of guanosine. This shows that UL97 kinase is the only additional gene product required to make vacc inia virus susceptible to GCV, and guanosine seems to be one natural s ubstrate for the enzyme. The system described here should be very help ful for fast and detailed functional analyses of UL97 mutations found in GCV-resistant HCMV isolates.