ROLES OF VACCINIA VIRUS RIBONUCLEOTIDE REDUCTASE AND GLUTAREDOXIN IN DNA PRECURSOR BIOSYNTHESIS

To examine the possible role of the vaccinia virus glutaredoxin as a c ofactor for viral ribonucleotide reductase, viral growth, DNA synthesi s, and dNTP pools were measured in infections of B-SC-40 monkey kidney cells with wild type vaccinia virus and with mutants of vaccinia that lacked a functional reductase or glutare-doxin. In infections of untr eated host cells, the lack of viral ribonucleotide reductase or glutar edoxin had only small effects upon virus growth. When host cells were pretreated with a-amanitin, which blocks host RNA polymerase II but no t viral transcription, viral DNA synthesis was markedly reduced in inf ections with either of the mutants when compared with wild type infect ions. Relative to dNTP levels in wild type infections, pools of dCTP, but not of the other dNTPs, were significantly reduced in infections o f amanitin-treated cells with either mutant, The parallel depletion of dCTP in the two mutants suggests that the role of glutaredoxin may be to function as a cofactor for viral ribonucleotide reductase. The dat a suggest that both viral proteins become essential for DNA replicatio n only when levels of the corresponding host cell proteins are deplete d.