THE BIOSYNTHESIS OF DEOXYGUANOSINE TRIPHOSPHATE (dGTP) IN HERPES SIMPLEX TYPE-1 (HSV-1) INFECTED VERO CELL TREATED WITH ACYCLOVIR (ACV) AND HYDROXYUREA (HU): 109

Abstract

Purine deoxynucleoside triphosphate pools increased dramatically in HSV-1 infected vero cells treated with ACV. This study quantitatively compares the contributions of the ribonucleotide reductase (RR) and deoxyguanosine salvage pathways for the biosynthesis of dGTP in HSV-1 infected cells. [14C]Guanine introduced 1 hr after infection was readily incorporated into dGTP and HSV DNA. By 6-8 hrs after treatment with ACV at 100 μM, both dATP and dGTP pools increased 7 fold and [14C]dGTP accumulated 32 fold over untreated infected controls. The increase in [14C]dGTP, dGTP and dATP in the presence of ACV was prevented by HU at 10 mM, which inhibits RR. By prelabeling cellular DNA with [5'-3H]deoxyguanosine prior to infection, it was possible to show that salvage of deoxyguanosine, derived from host DNA, was a minor pathway for dGTP syntheis during infection, and that HU had no effect on this process. Greater than 99% of the dGTP in infected ACV treated cells was derived from the guanine ribonucleotide pool through the RR reaction, as compared with <1% of the dGTP being derived from the salvage of endogenous deoxyguanosine formed from [5'-3H]-labeled cellular DNA.