A carboxyl-terminal peptide of the DNA-binding protein ICP8 of herpes simplex virus contains a single-stranded...

The DNA-binding protein ICP8 of herpes simplex virus is a multifunctional protein which is required for viral replication. To identify the single-stranded DNA-binding domain of the protein, recombinant plasmids containing the 5' or 3' coding portion of the ICP8 gene or the intact gene were constructed and transcribed using SP6 RNA polymerase. The resulting RNA was translated in vitro to produce a 62,000-Da amino-terminal peptide, a 69,000-Da carboxyl-terminal peptide, or the intact protein. When these were analyzed by single-stranded DNA-cellulose column chromatography, large amounts of the intact ICP8 bound to the columns while small amounts of the carboxyl-terminal peptide and undetectable amounts of the amino-terminal peptide bound. The majority of the carboxyl-terminal peptide which bound eluted from the columns with the same salt concentration as the intact ICP8. The in vitro synthesized intact protein had the same affinity for single-stranded DNA-cellulose as ICP8 purified from infected cells. These results suggest that the carboxyl-terminal portion of ICP8 contains a single-stranded DNA-binding site.