Herpes simplex virus type 2 induces S-phase entry and arrest to regulate the cell cycle for efficient replication.

Viruses often hijack core host cell processes to optimize their replication. In the current study, we conducted comparative proteomics analyses of epithelial cells infected by the prevalent human pathogen herpes simplex virus type 2 (HSV-2), followed by experimental validation. The results reveal that HSV-2 infection induces significant reprogramming of the host cell cycle, characterized by a pronounced accumulation of cells in the synthesis (S)-phase. Mechanistically, we discovered that HSV-2 promotes gap 1 (G1)/S transition by downregulating the cyclin-dependent kinase inhibitor p21 via a proteasome-mediated pathway. Following this, the virus induces S-phase cell cycle arrest, characterized by reduced levels of cyclin-dependent kinase 2 (CDK2) and its active phosphorylated form and decreased activity of the cyclin A2-CDK2 complex. Consequently, this dysfunctional 'pseudo-S-phase' state significantly enhances HSV-2 replication. These findings reveal a previously unrecognized dual mechanism employed by HSV-2 to manipulate the host cell cycle, thereby advancing our understanding of how pathogens disrupt cellular homeostasis to facilitate their replication.