Structure of Rift Valley Fever Virus RNA-Dependent RNA Polymerase

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• Rift Valley fever virus (RVFV) is a significant zoonotic arbovirus causing severe disease in humans and livestock.
• The RVFV L protein (RNA-dependent RNA polymerase, RdRp) is crucial for viral replication and transcription and represents a key drug target.

Purpose of the Study:

• To establish an expression system and purification protocol for the full-length RVFV L protein.
• To determine the cryo-electron microscopy (cryo-EM) structure of the RVFV L protein.
• To investigate the mechanism of RNA synthesis initiation by the RVFV L protein.

Main Methods:

• Expression and purification of full-length RVFV L protein.
• Cryo-electron microscopy (cryo-EM) for structural determination at 3.6 Å resolution.
• Biochemical assays to analyze RNA synthesis initiation.

Main Results:

• The first structure of a Phlebovirus genus L protein was determined.
• The RVFV L protein structure reveals unique features, including a distinct priming loop with significant movement.
• Structural and biochemical data demonstrate that a single template can initiate RNA synthesis, enhanced by 5' viral RNA.

Conclusions:

• The determined RVFV L protein structure provides novel insights into the RdRp mechanism within the Phlebovirus genus.
• Understanding the unique structural and functional aspects of the RVFV L protein is crucial for developing targeted antiviral therapies.
• This study lays the groundwork for designing inhibitors targeting RVFV RNA synthesis.