EXPRESSION OF THE MUTAGENIC PEPTIDE OF HERPES-SIMPLEX VIRUS TYPE-1 INVIRUS-INFECTED CELLS

A fragment of DNA from within the minimum transforming region (mtr-1) of herpes simplex virus type 1 (HSV-1) is known to raise the mutation frequency of cells. This activity has been attributed to a viral prote in whose properties are largely unknown. Antiserum was raised to a syn thetic peptide of a predicted amino acid sequence from the protein, an d was found to react with cells that were infected by HSV-1 in an ELIS A and by immunocytochemical staining. A combination of immunoprecipita tion and immunoblotting techniques confirmed that the epitope is locat ed at the carboxy terminus of the UL26 gene product and is downstream of epitopes that are recognized by two monoclonal antibodies. The muta genic peptide was different from the conventional gene product of UL26 in that: (a) It was expressed from a different reading frame, (b) It was expressed earlier in infection, and (c) It bound DNA, and thus cou ld be separated by DNA-cellulose chromatography. An RT-PCR experiment revealed two deletions in the cDNA, suggesting that RNA splicing could account for the frameshift. Examination of the DNA sequence of the re gion also revealed a potential ribosomal frame-shift site. The mutagen ic peptide of HSV-1 is therefore a product of the UL26 gene which is e xpressed with a different carboxy terminus early in infection, and thi s could be due either to RNA splicing or to ribosomal frame-shifting.