The cellular Notch1 protein promotes KSHV reactivation in an Rta-dependent manner.

Area of Science:

• Virology
• Cellular Biology
• Signal Transduction

Background:

• The Notch signaling pathway is implicated in Kaposi's sarcoma-associated herpesvirus (KSHV) infections and pathogenesis.
• RBP-Jk, a key component of the Notch pathway, interacts with the viral protein Rta during KSHV reactivation.

Purpose of the Study:

• To investigate the role of constitutive Notch activity in KSHV reactivation and viral pathogenesis.
• To elucidate the mechanism by which Notch signaling influences KSHV production.

Main Methods:

• Utilized a quantitative reporter virus system to assess Notch isoforms' ability to reactivate KSHV.
• Employed gamma-secretase inhibitor (GSI) and dominant-negative MAML1 to inhibit Notch signaling.
• Used siRNA to specifically inhibit Notch1 and analyzed viral transcription and infectious KSHV production.

Main Results:

• Constitutive Notch activity is essential for robust production of infectious KSHV.
• Inhibition of Notch signaling significantly reduced KSHV production and specific viral gene transcription.
• Activated Notch1 forms promoter-specific complexes with viral DNA during reactivation, cooperating with Rta.

Conclusions:

• Constitutive Notch activity is required for efficient KSHV reactivation and production.
• Activated Notch1 acts as a pro-viral factor, collaborating with Rta, MAML1, and RBP-Jk in a viral DNA complex.
• Notch signaling represents a critical host factor manipulated by KSHV for its life cycle.