Sequential structures provide insights into the fidelity of RNA replication

Area of Science:

• Virology
• Structural Biology
• Biochemistry

Background:

• RNA virus replication relies on viral RNA-dependent RNA polymerases, which exhibit low fidelity.
• Mutagenic ribonucleoside analogs can further reduce replication fidelity, leading to lethal mutagenesis and virus extinction.

Purpose of the Study:

• To elucidate the structural mechanisms underlying RNA replication fidelity in foot-and-mouth disease virus (FMDV).
• To investigate the interactions of FMDV polymerase with natural substrates and mutagenic analogs at a molecular level.

Main Methods:

• X-ray crystallography was used to determine the structures of four elongation complexes of FMDV polymerase 3D.
• Complexes were formed with natural substrates (ATP, UTP) or mutagenic nucleotides (ribavirin triphosphate, 5-fluorouridine triphosphate) and various RNA template-primers.

Main Results:

• The structures captured distinct RNA synthesis events within crystals, revealing key amino acid roles.
• Identified critical interactions in nucleotide/analog recognition, template base positioning, and primer 3'-OH group positioning.
• Provided atomic-level insights into the molecular basis of FMDV polymerase's low fidelity.

Conclusions:

• The study defines key interactions governing viral RNA replication and fidelity.
• Structural insights explain the molecular basis for the low fidelity of viral RNA polymerases, particularly in the context of mutagenic analog incorporation.