RNA virus polymerase-helicase coupling enables rapid elongation through duplex RNA.

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Positive-sense single-stranded RNA ((+)RNA) viruses encode essential helicases, like the coronavirus (CoV) nsp13-helicase.
• The precise function of nsp13-helicase during CoV replication remains largely unknown despite its essential role.

Purpose of the Study:

• To elucidate the specific role and mechanism of the CoV nsp13-helicase in viral RNA synthesis.
• To investigate the interaction between nsp13-helicase and the CoV polymerase.

Main Methods:

• Magnetic tweezers utilized to study the real-time interaction and translocation of nsp13-helicase on RNA.
• Kinetic modeling employed to analyze the energy landscape and mechanochemistry of the nsp13-helicase-polymerase complex.

Main Results:

• Nsp13-helicase specifically associates with the CoV polymerase and translocates on the strand opposite to the template.
• Nsp13-helicase significantly increases the RNA synthesis rate on double-stranded RNA templates by tenfold.
• The enzyme employs both ATP hydrolysis and allosteric regulation to facilitate polymerase progression through dsRNA structures.

Conclusions:

• Demonstrates a novel function for (+)RNA virus helicases in assisting viral RNA synthesis.
• Provides a deeper understanding of the mechanisms underlying CoV replication and transcription.