Characterization and Mapping of Equine Herpesvirus Type 1 Immediate Early, Early, and Late Transcripts

Northern blot analysis was used to characterize and map equine herpesvirus type 1 (EHV-1) immediate early (IE), early, and late transcripts. Genomic EHV-1 DNA and cloned EHV-1 restriction endonuclease fragments, representing the entire genome, were 32P-labeled and hybridized to immobilized total cell RNA isolated from EHV-1 infected rabbit kidney cells incubated in the presence or absence of metabolic inhibitors. A single 6.0 kilobase (kb) IE transcript mapped to viral inverted repeat sequences. Approximately 41-45 early transcripts ranging in size from 0.8 to 6.4 kb and 18-20 late transcripts ranging in size from 0.8 to 10.0 kb were identified. These findings demonstrate that EHV-1 gene expression is regulated at the level of transcription, although regulation at the level of translation is also possible. The results provide a basis for examining alterations in viral gene expression in EHV-1 oncogenically transformed and persistently infected cells.