The extreme carboxyl terminus of the equine herpesvirus 1 homolog of herpes simplex virus VP16 is essential for immediate-early gene activation.
Gene 12 of equine herpesvirus 1 (EHV-1), the homolog of herpes simplex virus (HSV) VP16 (alpha TIF, Vmw65), was cloned into a eukaryotic expression vector by PCR and used in transactivation studies of both the EHV-1 and HSV-1 IE1 promoters. Results demonstrated that the product of gene 12 is a potent transactivator of immediate-early gene expression of both viruses, which requires sequences in the upstream HSV-1 promoter for activity. Mutational analysis of the gene 12 open reading frame indicated that removal of the C-terminal 7 amino acids, which contain a short region of homology with the extreme C terminus of VP16, inactivated the protein. Within this region, only a single methionine residue appeared to be essential for activity, implying that gene 12 may have a modular array of organization similar to that of VP16. However, fusion of the gene 12 C terminus to a truncated form of VP16, which contained the complex formation domain, did not restore activity to the HSV-1 protein. These data demonstrate that the EHV-1 immediate-early transactivator may not be functionally colinear with VP16, with transactivation requiring both the C terminus and another region(s) present within the N-terminal portion.
Department of Microbiology, University of Leeds, United Kingdom.
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Elliott
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004279:DNA, Viral; D015967:Gene Expression Regulation, Viral; D017405:Herpes Simplex Virus Protein Vmw65 / Q000737:chemistry / Q000235:genetics*; D004861:Herpesvirus 1, Equid / Q000235:genetics*; D017874:Immediate-Early Proteins / Q000235:genetics*; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D017385:Sequence Homology; D015533:Transcriptional Activation; D014709:Vero Cells
D004279:DNA, Viral; D017405:Herpes Simplex Virus Protein Vmw65; D017874:Immediate-Early Proteins; D008715:Methionine