AP-1 cis-response elements are involved in basal expression and Vmw110 transactivation of the large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10).

The promoter of the large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10) has two AP-1 cis-response elements, respectively located at positions -62 and -94 relative to the transcription start site (Wymer et al., 1989. J. Virol. 63, 2773-2784). Chloramphenicol acetyl transferase (CAT) analysis with hybrid constructions of the CAT structural gene and the ICP10 promoter or its mutants and gel retardation studies were used to examine the role of the AP-1 cis-response elements in expression from the ICP10 promoter. Basal expression from the wild-type promoter was significantly (75-90%) reduced by mutation of the upstream or downstream AP-1 element. Mutation in the upstream AP-1 element also caused a 60% reduction in c-Jun-mediated activation. Activation was decreased 40% by mutation in the downstream AP-1 element and it was abrogated by mutation of both elements. Similar results were obtained for ACT-deleted mutants and mutants in which CT was mutated to AG. The trans-activation by Vmw110 was also reduced by mutation of the AP-1 elements (10- and 2-fold for the upstream and downstream element, respectively) and it was abrogated by mutation of both AP-1 elements. Mutation of nucleotides adjacent to the AP-1 cis-response elements had no effect on trans-activation. Gel retardation assays with a DNA probe representing the wild-type ICP10 promoter and nuclear extracts from HSV-1-infected cells identified one complex that was not seen with mock-infected cells or with cells infected with a Vmw110-deleted mutant. The complex was not seen when HSV-1-infected cells were reacted with an AP-1-mutant DNA probe, and its formation was competed by an AP-1 but not a mutant AP-1 oligonucleotide. The migration of this complex was retarded by c-Fos antibody, suggesting that both AP-1 and Vmw110 are involved in its formation. A mutant deleted in all sequences upstream of the TATA box was also activated by Vmw110, but this activation was only 2-fold lower than that seen for the wild type and significantly higher (10-fold) than that seen for the double AP-1 mutants. The data suggest that AP-1 elements play a crucial role in ICP10 gene expression/activation.