Immediate-early protein ICP4 (ICP4)

Immediate-early protein ICP4 is a critical regulatory protein encoded by the Herpes Simplex Virus (HSV-1 and HSV-2) that functions as a multifunctional transcription factor (UniProt: P08392). It is essential for the viral life cycle, as it coordinates the transition from immediate-early to early and late gene expression by recruiting host cellular transcription factors and RNA polymerase II to viral promoters (PubMed: 11836334). ICP4 also acts as a repressor of its own synthesis and other immediate-early genes, maintaining a balanced viral environment during infection. Because of its indispensable role in viral replication and its lack of a direct human homolog, ICP4 is a high-priority target for the development of novel antiviral therapies, including small molecule inhibitors and gene-editing tools like CRISPR/Cas9 (PubMed: 27535030). Targeting ICP4 aims to halt the progression of HSV infections, which can range from common cold sores to severe conditions like encephalitis or keratitis. Current research focuses on disrupting its DNA-binding domain or its ability to interact with the host's transcriptional machinery to prevent the formation of new viral progeny.

Other names

Infected cell protein 4Vmw175IE175RS1Alpha-4 proteinTranscriptional activator IE175

Inhibition of viral immediate-early gene expression and subsequent replication cycles by blocking the recruitment of host RNA polymerase II or preventing DNA binding to viral promoters (PubMed: 25653445).