Influenza virus endoribonuclease

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• The influenza virus polymerase complex, comprising PB1, PB2, and PA subunits, possesses endoribonuclease and RNA-dependent RNA polymerase activities.
• These enzymatic activities have historically required the complete three-subunit complex for observation.

Purpose of the Study:

• To describe a robust procedure for purifying the active influenza virus polymerase complex with genomic RNA and nucleoprotein.
• To synthesize capped RNA substrates for studying the influenza virus endonuclease.
• To characterize the enzymatic properties of the influenza virus endoribonuclease using a model RNA substrate.

Main Methods:

• Purification of the influenza virus polymerase complex from viral particles.
• Synthesis of capped RNA molecules (G20 RNA) as endonuclease substrates.
• Enzymatic assays under steady-state and single-turnover conditions to determine kinetics and metal ion dependencies.

Main Results:

• Optimized conditions allow for the study of the chemical step of RNA cleavage under single turnover.
• The endonuclease activity is dependent on divalent metal ions, with Mn(II), Co(II), and Fe(II) being highly efficient.
• Slow binding of Zn(II) and Ni(II) suggests conformational changes are necessary for activity with these ions. DOC detergent inhibits activity and disrupts the complex.

Conclusions:

• The study provides a refined method for purifying and assaying the influenza virus endonuclease.
• Characterization reveals specific metal ion requirements and kinetic properties, including product dissociation limitations.
• Understanding these enzymatic activities is crucial for comprehending influenza virus replication and for potential therapeutic target development.