The equine herpesvirus type 1 immediate-early gene product contains an acidic transcriptional activation domain.
The equine herpesvirus type 1 (EHV-1) immediate-early (IE) gene product, an ICP4 homolog, is the major regulatory protein encoded by EHV-1 during cytolytic infection. The IE gene product has been demonstrated to induce reporter gene expression directed by both homologous and heterologous viral promoters, including the EHV-1 thymidine kinase (tk) promoter, the herpes simplex virus type 1 (HSV-1) tk and ICP4 promoters, and the simian virus 40 early promoter. In this report, the transcriptional activation domain of the EHV-1 IE gene product was mapped to within an acidic, 87-amino-acid region (amino acids 3 to 89) at the amino-terminus of the IE molecule. It is demonstrated that the IE transcriptional activation domain, when fused to the DNA-binding domain of the yeast transcriptional activator GAL4, can activate gene expression in cell lines derived from at least two different species. Moreover, it is shown that the EHV-1 IR2 gene product (Harty and O'Callaghan, J. Virol. 65, 3829-3838, 1991), a truncated form of the IE polypeptide lacking IE amino acid residues 1-322 (and, therefore lacks the deduced transcriptional activation domain), fails to transactivate the EHV-1 tk promoter, but retains the ability to down-regulate the EHV-1 IE promoter. Fusion of the acidic transcriptional activation domain of the HSV-1 virion protein VP16 to the transactivation-deficient IR2 gene product restored the ability of this truncated IE polypeptide to transactivate the EHV-1 tk promoter. These findings suggest a role for the IR2 protein as a trans-repressor of EHV-1 gene expression.
Smith
R H
RH
Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932.
Zhao
Y
Y
O'Callaghan
D J
DJ
D000595:Amino Acid Sequence; D004861:Herpesvirus 1, Equid / Q000235:genetics*; D017874:Immediate-Early Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation; D014764:Viral Proteins / Q000235:genetics
C050678:IE1 protein, Human herpesvirus 1; D017874:Immediate-Early Proteins; D014157:Transcription Factors; D014764:Viral Proteins