Segment-specific terminal sequences of Bunyamwera bunyavirus regulate genome replication

Area of Science:

• Virology
• Molecular Biology
• RNA Virus Replication

Background:

• Bunyamwera virus (BUNV) is the prototype for the Orthobunyavirus genus and Bunyaviridae family, characterized by a segmented negative-sense RNA genome.
• The BUNV genome comprises three segments: small (S), medium (M), and large (L), which are involved in transcription and replication processes.
• Previous methods using reporter gene assays could not effectively differentiate between RNA replication and transcription activities.

Purpose of the Study:

• To develop a direct metabolic labeling method for identifying BUNV RNA replication and transcription products.
• To compare the RNA replication abilities of the S, M, and L BUNV segments.
• To identify specific sequence elements responsible for differential segment replication efficiency.

Main Methods:

• Modification of a cDNA-derived RNA synthesis system for direct metabolic labeling of BUNV RNA.
• Generation of genome analogs containing terminal sequences of S, M, and L segments.
• Analysis of synthesized RNAs to distinguish replication and transcription activities and compare segment efficiencies.

Main Results:

• Direct RNA analysis enabled differentiation between RNA replication and mRNA transcription, overcoming limitations of previous reporter gene assays.
• The relative RNA replication abilities of BUNV segments were determined as M > L > S.
• A 12-nucleotide region at both the 3' and 5' termini of the M segment was identified as crucial for its high replication ability.

Conclusions:

• The modified direct RNA analysis system provides a robust method for studying BUNV RNA metabolism.
• Segment-specific terminal sequences significantly influence the replication efficiency of BUNV RNA segments.
• The M segment possesses intrinsically higher replication capabilities, mediated by specific terminal nucleotide sequences.