Herpes simplex virus 1 (HSV-1) virions, like those of all herpesviruses, contain a protein layer termed the tegument localized between the capsid and the envelope. Here we show that ICP27 alone can up-regulate gene expression of a retroviral vector containing Moloney murine leukemia virus (MoMuLV) regulatory sequences. To investigate the block to virus replication, we used the HSV-1 triple mutant in1820K, which, under appropriate conditions, is effectively devoid of the transactivators VP16 (a virion protein), ICP0, and ICP4 (both IE proteins). Functional ICP4 is required for enhanced transcriptional activation in the transient expression assay system. The basis for the dominance of the syn− allele in the delayed infection is not known. Furthermore, genomic end-specific restriction fragments were not detected in DNA purified from noncomplementing cells infected with HSV-1(deltaU(L)17) or HSV-1(U(L)17-stop), whereas end-specific fragments were readily detected when the viruses were propagated on complementing cells. A BAL31 mutation deleting the upstream open reading frame of pol had no effect on biological activity in a complementation assay but was found to increase the efficiency of in vitro translation of pol RNA.
Two amino-terminal deletions of 27 and 67 residues were found to greatly enhance the enzymatic activity of the in vitro translated product, while all carboxy-terminal deletions examined (the smallest being 164 residues) abolished in vitro enzymatic activity. As previously described (Ulmer et al., 1994), DNA vaccines constructed using NP or M genes can induce cross-protective immunity. An antiserum prepared against this fusion protein precipitated the 140-kilodalton DNA polymerase from herpes simplex virus type 1-infected cell lysates.