CLONING, SEQUENCING, AND FUNCTIONAL-CHARACTERIZATION OF THE 2 SUBUNITS OF THE PSEUDORABIES VIRUS DNA POLYMERASE HOLOENZYME - EVIDENCE FOR SPECIFICITY OF INTERACTION

The pseudorabies virus (PRV) genes encoding the two subunits of the DN A polymerase were located on the genome by hybridization to their herp es simplex virus type 1 (HSV-1) homologs, pol and UL42, and subsequent ly were sequenced. Like the HSV-1 homologs, in vitro translation produ cts of the PRV gene encoding the catalytic subunit (pol) possessed act ivity in the absence of the Pol accessory protein (PAP). However, the PRV PAP stimulated the activity of Pol fourfold in the presence of 150 mM KCl, using an activated calf thymus DNA template. The stimulation of Pol activity by PAP under high-salt conditions and the inhibition o f Pol activity by PAP when assayed in low salt (0 mM KCl) together wer e used to determine the specificity with which PAP interacted with pol . Despite functional similarity, HSV-1 UL42 and PRV PAP could neither stimulate the noncognate Pols at high salt nor inhibit them at low sal t. Furthermore, a PRV Pol mutant lacking the 30 C-terminal amino acids retained basal pol activity but could be neither stimulated nor inhib ited by the PRV PAP. Sequence comparisons of the pol proteins of the a lphaherpesviruses reveal a conserved domain in the C terminus which te rminates immediately before the last 41 residues of both PRV and HSV-1 proteins. These results indicate that the ability and specificity for interaction of the PRV Pol with PAP most likely resides predominantly in the extreme Pol C terminus.