SEQUENCE AND TRANSCRIPTIONAL ANALYSIS OF THE GUINEA-PIG CYTOMEGALOVIRUS DNA-POLYMERASE GENE

Although the guinea-pig cytomegalovirus (GPCMV) displays a similar pat hogenesis to human cytomegalovirus (HCMV), there have unfortunately be en few molecular analyses of the GPCMV genome to date. The guinea-pig has proved useful for the testing of drugs active against CMV infectio n, and insights derived from characterization of the specific virally encoded molecular targets of antiviral therapies would allow this mode l system to be more fully developed. Because the DNA polymerase serves as an important target for nucleoside antiviral agents active against herpesviruses, experiments were undertaken to identify, clone and seq uence the GPCMV DNA polymerase gene (pol). A 3285 bp ORF capable of en coding a 1094 amino acid protein was identified spanning portions of t he HindIII Q and P fragments of the genome. This ORF contained extensi ve homology to other herpesvirus DNA pol genes. Northern blot analyses identified two 3' coterminal pol-specific mRNAs of 3.9 and 1.9 kb at early times postinfection. Primer extension and nuclease protection an alyses mapped the 5' end of the 3.9 kb transcript to a site 275 bases upstream of the pol initiation codon. Comparison of the GPCMV pol-enco ded sequence to those of other herpesvirus polymerases identified nonc onservative amino acid substitutions in a domain involved in substrate recognition.