The acidic amino-terminal region of varicella-zoster virus open reading frame 4 protein is required for transactivation and can functionally replace the corresponding region of herpes simplex virus ICP27.
Both varicella-zoster virus open reading frame 4 (ORF4) protein and its herpes simplex virus type 1 homolog ICP27 have highly acidic amino-terminal regions and cysteine-rich carboxy-terminal regions. To investigate the functional domains of these proteins, mutants were constructed and their transregulatory functions were tested in transient expression assays using two reporter plasmids, pTK-CAT-SV40A and pTK-CAT-synA, containing the same promoter sequences but different mRNA processing signals. ORF4 transactivates both pTK-CAT-SV40A and pTK-CAT-synA, while ICP27 transrepresses pTK-CAT-SV40A and transactivates pTK-CAT-synA. Deletion of the ORF4 amino-terminal region abolished most of the transactivating activity for pTK-CAT-synA but retained most of the transactivating activity for pTK-CAT-SV40A. Construction of chimeric ORF4-ICP27 molecules indicated that the ORF4 amino-terminal region was able to replace the corresponding region of ICP27 which is required for both transrepression of pTK-CAT-SV40A and transactivation of pTK-CAT-synA. Similarly, the ICP27 amino-terminal region was able to partially replace the corresponding region of ORF4 which is required for transactivation of pTK-CAT-synA Thus, while ORF4 and ICP27 have different properties in transient expression assays, the amino-terminal regions of ORF4 and ICP27 are functionally homologous to each other and are important in regulating gene expression.
Moriuchi
M
M
Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892, USA.
Moriuchi
H
H
Debrus
S
S
Piette
J
J
Cohen
J I
JI
D000595:Amino Acid Sequence; D015967:Gene Expression Regulation, Viral; D018259:Herpesvirus 1, Human / Q000502:physiology*; D014645:Herpesvirus 3, Human / Q000502:physiology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D015534:Trans-Activators / Q000235:genetics; D015533:Transcriptional Activation; D014764:Viral Proteins; D014779:Virus Replication / Q000235:genetics
C057120:ICP27 protein, human herpesvirus 1; D017874:Immediate-Early Proteins; C085824:ORF4 protein, Human herpesvirus 3; D015534:Trans-Activators; D014764:Viral Proteins