Oncogenic Herpesvirus Utilizes Stress-Induced Cell Cycle Checkpoints for Efficient Lytic Replication

Area of Science:

• Virology
• Molecular Biology
• Oncology

Background:

• Kaposi's sarcoma herpesvirus (KSHV) establishes latent infections and reactivates lytic replication in a subset of tumor cells.
• KSHV reactivation is crucial for viral spread and disease progression in Kaposi's sarcoma and lymphoproliferative disorders.

Purpose of the Study:

• To identify novel regulators of KSHV reactivation using a siRNA screen.
• To elucidate the molecular mechanisms by which host cell stress influences KSHV lytic replication.

Main Methods:

• Conducted a siRNA screen to identify KSHV reactivation regulators.
• Investigated the role of MDM2 and p53 pathways in KSHV lytic replication.
• Analyzed cell cycle progression and viral replication dynamics upon gene depletion.

Main Results:

• Identified MDM2, an E3 ubiquitin ligase and p53 repressor, as a negative regulator of KSHV reactivation.
• Depletion of MDM2 enhanced KSHV lytic transcription and viral reactivation.
• KSHV lytic replication induced a p53 response, DNA damage, and G2 cell cycle arrest.
• Depletion of p21, a p53 target, restored cell cycle progression, impaired viral reactivation, and delayed cytopathic effects.

Conclusions:

• MDM2 acts as a gatekeeper, suppressing KSHV lytic replication.
• KSHV exploits host cell stress responses, particularly the p53 pathway, to facilitate efficient lytic replication.
• Understanding these host-virus interactions offers potential therapeutic targets for KSHV-driven diseases.