High level expression in 293 cells of the herpes simplex virus type 2 ribonucleotide reductase subunit 2 using an adenovirus vector

The herpes simplex viruses (HSV-1 and HSV-2) encode a ribonucleotide reductase consisting of two non-identical subunits (RR1 and RR2) which associate to form the active holoenzyme. To facilitate the purification and subsequent biochemical characterization of this enzyme, we have cloned the small subunit 2 of the HSV-2 ribonucleotide reductase (RRHSV-2 2) in a helper-independent adenovirus type 5 vector under the control of the adenovirus type 2 major late promoter. After infection of 293 cells with the recombinant virus, the amount of RRHSV-2 2 protein produced was eightfold higher than in HSV-2-infected cells. The specific activities of the RRHSV-2 2 recombinant subunit and the RRHSV-2 2 protein in HSV-2-infected cells were determined by their mixing with saturating amounts of isolated RRHSV-1 1 subunit. By comparison of the relative amount of each RRHSV-2 2 subunit with its specific activity, we calculated that the recombinant protein intrinsic activity was similar to that of the protein produced in HSV-2-infected cells. These results demonstrated that the adenovirus expression vector is a good system to produce an active RRHSV-2 2 subunit in fairly high amounts.