ANALYSIS OF THE COMPLETE DNA-SEQUENCE OF MURINE CYTOMEGALOVIRUS

The complete DNA sequence of the Smith strain of murine cytomegaloviru s (MCMV) was determined from virion DNA by using a whole-genome shotgu n approach. The genome has an overall G+C content of 58.7%, consists o f 230,278 bp, and is arranged as a single unique sequence with short ( 31-bp) terminal direct repeats and several short internal repeats. Sig nificant similarity to the genome of the sequenced human cytomegalovir us (HCMV) strain AD169 is evident, particularly for 78 open reading fr ames encoded by the central part of the genome. There is a very simila r distribution of G+C content across the two genomes. Sequences toward the ends of the MCMV genome encode tandem arrays of homologous glycop roteins (gps) arranged as two gene families. The left end encodes 15 g ps that represent one family, and the right end encodes a different fa mily of 11 gps. A homolog (m144) of cellular major histocompatibility complex (MHC) class I genes is located at the end of the genome opposi te the HCMV MHC class I homolog (UL18). G protein-coupled receptor (GC R) homologs (M33 and M78) occur in positions congruent with two (UL33 and UL78) of the four putative HCMV GCR homologs. Counterparts of all of the known enzyme homologs in HCMV are present in the MCMV genome, i ncluding the phosphotransferase gene (M97), whose product phosphorylat es ganciclovir in HCMV-infected cells, and the assembly protein (M80).