Structure-based mechanism of action of a viral poly(ADP-ribose) polymerase 1-interacting protein facilitating virus...

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Poly(ADP-ribose) polymerase 1 (PARP-1) regulates cellular functions and inhibits oncogenic gammaherpesvirus replication by targeting the replication and transcription activator (RTA).
• Murine gammaherpesvirus 68 (MHV-68) encodes a viral PARP-1-interacting protein (vPIP) that promotes viral replication by interfering with PARP-1 and RTA interactions.

Purpose of the Study:

• To determine the structure of MHV-68 vPIP.
• To elucidate the molecular mechanism by which vPIP facilitates viral replication by interacting with PARP-1.
• To investigate the conserved function of vPIPs in gammaherpesviruses.

Main Methods:

• X-ray crystallography was used to determine the 2.2 Å resolution structure of MHV-68 vPIP.
• Structure-based mutagenesis identified key residues and regions essential for vPIP's nuclear localization, PARP-1 interaction, and function.
• Recombinant MHV-68 mutants were generated to assess viral replication in vitro and in vivo.

Main Results:

• The MHV-68 vPIP structure revealed 12 α-helices and N-terminal β-strands forming a V-shaped dimer.
• The N-terminal β-strands and α1 helix are critical for vPIP's nuclear localization and function.
• Mutations in three specific residues (Phe5, Ser12, Thr16) abolished vPIP's interaction with PARP-1 and severely attenuated viral replication.
• ORF49 from Kaposi's sarcoma-associated herpesvirus also interacted with PARP-1, suggesting a conserved mechanism.

Conclusions:

• MHV-68 vPIP utilizes a specific structural interface, including N-terminal residues, to interact with PARP-1.
• This interaction disrupts PARP-1's function, enabling oncogenic gammaherpesvirus replication.
• vPIPs represent a conserved viral strategy to overcome host antiviral defenses mediated by PARP-1.