Role of the human herpesvirus 6 u69-encoded kinase in the phosphorylation of ganciclovir.
The human herpesvirus 6 (HHV-6) U69 gene product (pU69) is the presumed functional homolog of the human cytomegalovirus (HCMV) UL97-encoded kinase (pUL97), which converts ganciclovir to its monophosphate metabolite in HCMV-infected cells. It has been reported that insertion of U69 into baculovirus confers sensitivity to ganciclovir in insect cells (J Virol 73:3284-3291, 1999). Our metabolic studies in HHV-6-infected human T-lymphoblast cells indicated that the efficiency of ganciclovir phosphorylation induced by HHV-6 was relatively poor. Recombinant vaccinia viruses (rVVs), expressing high levels of pU69 from two HHV-6 strains (representing the A and B variant), were constructed and used to compare the ganciclovir-phosphorylating capacity of pU69 and pUL97 in human cells. Metabolic studies with [8-(3)H]ganciclovir showed that ganciclovir was phosphorylated in human cells infected with pU69-expressing rVVs, although the levels of phosphorylated ganciclovir metabolites were approximately 10-fold lower than those observed with pUL97. We also demonstrated that pU69, like pUL97, is expressed as a nuclear protein. Our results indicate that the limited phosphorylation of ganciclovir by pU69 may contribute to its modest antiviral activity against HHV-6 in certain cell systems.
De Bolle
Leen
L
Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium.
Michel
Detlef
D
Mertens
Thomas
T
Manichanh
Chaysavanh
C
Agut
Henri
H
De Clercq
Erik
E
Naesens
Lieve
L
D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000378:metabolism* / Q000494:pharmacology; D015774:Ganciclovir / Q000378:metabolism* / Q000494:pharmacology; D005814:Genes, Viral / Q000502:physiology; D015654:Herpesvirus 6, Human / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000821:virology; D014407:Tumor Cells, Cultured / Q000821:virology; D014616:Vaccinia virus / Q000187:drug effects / Q000235:genetics
D000998:Antiviral Agents; D011994:Recombinant Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C464753:pU69 kinase, human herpesvirus 6; D015774:Ganciclovir