ICP4
Domain
The N-terminal and C-terminal domains are required for the transcriptional activation function of ICP4.
Function
Plays an essential role in the regulation of viral gene expression by both activating and repressing host RNA polymerase II-mediated transcription. Binds with high affinity to the sequence 5'-ATCGTC-3'. Activates transcription by recruiting a form of the host TFIID to promoters and stabilizing the pre-initiation complex formation. Negatively regulates its own transcription. This immediate early (IE) protein is absolutely necessary for the transition from IE transcription to later viral gene transcription.
Post-translational modifications
ADP-ribosylated.
The long stretch of Ser is a major site of phosphorylation. Only the phosphorylated forms are capable of interacting with beta or gamma genes.
Sequence Similarities
Belongs to the herpesviridae ICP4 family.
Cellular localization
- Host nucleus
- Host cytoplasm
- Virion tegument
- Localizes to the cytoplasm when phosphorylated.
Alternative names
IE175, RS1, ICP4, Major viral transcription factor ICP4, Alpha-4 protein, Infected cell protein 4, Transcriptional activator IE175