A major transactivator of varicella-zoster virus, the immediate-early protein IE62, contains a potent N-terminal activation domain.
Accumulating evidence indicates that the product of the putative immediate-early gene ORF62 (IE62) activates varicella-zoster virus (VZV) genes thought to represent all three kinetic classes, namely, immediate-early (alpha), early (beta), and late (gamma) classes, of VZV genes as well as a variety heterologous gene promoters. However, the mechanism(s) by which IE62 protein mediates transactivation of these diverse VZV and heterologous gene promoters remains to be elucidated. In this study, by using yeast GAL4 protein chimeras, the coding regions of VZV ORF62 possessing activation domains have been assessed. We demonstrate that the VZV IE62 protein contains a potent activation domain in the N-terminal portion of the molecule, encoded within the first 86 codons of ORF62. The predicted secondary structure profile and the acid-base composition of this IE62 domain resemble those of other transregulatory proteins whose activation is mediated through acidic, hydrophobic elements. In addition, we show that deletion of this activation domain from the 1,310-residue native IE62 protein results in ablation of the transactivator function of IE62. We also present evidence that the mutant IE62 protein lacking the activation domain, though devoid of transactivation ability, was still capable of interfering with the activation of target promoters by the native, full-length IE62.
Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.
L P
LP
Perera
J D
JD
Mosca
W T
WT
Ruyechan
G S
GS
Hayward
S E
SE
Straus
J
J
Hay
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003062:Codon / Q000235:genetics; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D014645:Herpesvirus 3, Human / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015183:Restriction Mapping; D029701:Saccharomyces cerevisiae Proteins; D013601:T-Lymphocytes; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*
D003062:Codon; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C074221:IE62 protein, Human herpesvirus 3; D017874:Immediate-Early Proteins; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D014759:Viral Envelope Proteins