Acidic C terminus of vaccinia virus DNA-binding protein interacts with ribonucleotide reductase

Evidence from prokaryotic systems suggests that enzymes of dNTP synthesis are organized near the DNA replication apparatus, allowing direct utilization of dNTPs at their sites of synthesis. To investigate whether similar interactions exist within a eukaryotic environment, we have prepared anti-idiotypic antibodies to the small subunit of vaccinia virus ribonucleotide reductase, and we used these antibodies to search for proteins that interact with this enzyme. This approach identified a 34-kDa viral phosphoprotein, which, like ribonucleotide reductase itself, is localized within infected cells at DNA replication sites. After expression of its structural gene in Escherichia coli, the recombinant protein was purified and found (i) to bind tightly to single-stranded DNA and (ii) to stimulate enzymatic activity of vaccinia ribonucleotide reductase. These observations suggest a physical association between dNTP synthesis and DNA replication in this viral system.