The herpesvirus saimiri open reading frame (ORF) 50 (Rta) protein contains an at hook required for binding to the ORF 50 response element in delayed-early promoters.
Amino Acid Sequence
Gene Expression Regulation, Viral
Molecular Sequence Data
Herpesvirus 2, Saimiriine
Promoter Regions, Genetic
The herpesvirus saimiri open reading frame (ORF) 50 encodes two proteins, which activate transcription directly, following interactions with delayed-early (DE) promoters containing a specific motif. In this report, we demonstrate that ORF 50 contains a DNA binding domain that has homology to an AT hook DNA binding motif. Deletion analysis of this domain reduces ORF 50-mediated transactivation of the DE ORF 6 and ORF 57 promoters by 100 and 90%, respectively. Furthermore, gel retardation experiments demonstrated that the AT hook motif is required for binding the ORF 50 response element in the promoters of DE genes. Single site-directed mutagenesis of the AT hook revealed that mutation of the glycine residue at position 408 to an alanine reduces ORF 50 transactivation of the ORF 57 promoter by 40%. Moreover, the mutation of multiple basic residues in conjunction with the glycine residue within the core element of the AT hook abolishes ORF 50-mediated transactivation. In addition, p50GFPDeltaAT-hook is capable of functioning as a trans-dominant mutant, leading to a reduction in virus production of approximately 50% compared to that for wild-type ORF 50.