Nucleotide sequence analysis of a 21-kbp region of the genome of human herpesvirus-6 containing homologues of human cytomegalovirus major immediate-early and replication genes.

Human herpesvirus-6 (HHV-6) is a CD4+ T-lymphotropic herpesvirus that is a member of the betaherpesvirus subgroup. This laboratory has reported previously the results of large-scale sequence analyses of the HHV-6 genome and has identified putative immediate-early (IE) regulatory genes and associated transactivation functions. In this report I present the sequence analysis of a 21-kbp region of the genome of HHV-6 strain U1102 that is contiguous with the proximal region of the putative major IE (MIE) locus. Within this region (genomic positions 109-130 kbp) is a homologue of the human cytomegalovirus (HCMV) IE2 MIE gene (UL122), in addition to genes encoding probable virus DNA replication functions. The latter include components of the helicase-primase complex, corresponding to HCMV UL102 and UL105 gene products, and a homologue of the origin binding protein conserved among the alphaherpesviruses. Several genes unique to HHV-6 also have been identified within the sequenced locus. These findings will contribute to efforts to identify and functionally characterize the complete repertoire of HHV-6 transcriptional regulatory genes and will provide a basis for the further analysis of the molecular biology of this betaherpesvirus.