Infected cell protein 27 (ICP27)

Infected cell protein 27 (ICP27) is an essential regulatory protein encoded by the herpes simplex virus type 1 (HSV-1) RL2 gene and has homologs in all herpesviruses[4][5][7]. ICP27 is a multifunctional, predominantly nuclear, RNA-binding protein that performs several critical roles in the HSV-1 lifecycle, including the inhibition of host cell pre-mRNA splicing, suppression of host transcription termination, and export of intronless viral mRNAs from the nucleus[1][2][3][4][5][8]. Structurally, ICP27 consists of a disordered N-terminal region and a conserved C-terminal globular ICP27 homology domain, which mediates dimerization essential for its functions[5]. Key domains include an RGG box for RNA binding and a nuclear export sequence[4][5]. ICP27 interacts with multiple cellular factors involved in RNA processing (CPSF complex, splicing proteins, mRNA export machinery), recruits RNA polymerase II to viral replication sites, aids in translation of late viral genes, and modulates stress and apoptotic pathways[1][2][4][5][6][7]. ICP27 is not a human therapeutic target or a classical drug target (such as a receptor, enzyme, transporter) but is a viral protein critical for herpesvirus replication and pathogenesis[3][4][7]. It is essential for HSV-1 viability, functions as an immediate-early regulatory protein, and is required for efficient expression of late viral genes[7][9]. ICP27 mediates export of intronless viral mRNAs[4][5] and inhibits host cell mRNA 3′ processing, transcription termination, and splicing, contributing to host shutoff[1][2][3][8]. It binds GC-rich RNAs and interacts with many cellular RNA processing proteins[4][5]. ICP27 also has roles in nuclear-cytoplasmic shuttling and has been implicated in stress/apoptotic responses and cell cycle regulation[2][4][9]. The C-terminal region is critical for many of its interactions and essential functions[1][5][6].

Other names

HSV-1 ICP27Herpes simplex virus ICP27Infected cell protein 27RL2 gene product