Kissing interaction between 3' noncoding and coding sequences is essential for porcine arterivirus RNA replication.

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Porcine reproductive and respiratory syndrome virus (PRRSV) causes significant economic losses in the swine industry.
• Understanding PRRSV replication mechanisms is crucial for developing effective control strategies.

Purpose of the Study:

• To identify essential replication elements within the PRRSV genome, specifically in the region encoding structural proteins.
• To elucidate the role of ORF7 and its encoded nucleocapsid protein in viral RNA replication.

Main Methods:

• Utilized an infectious cDNA clone of PRRSV for genetic manipulation.
• Performed deletion analysis within ORF7 to identify critical nucleotide sequences.
• Employed strand-specific reverse transcription-PCR to analyze viral RNA synthesis.
• Investigated RNA secondary structures (hairpins) and their interactions (kissing loop) using mutational analysis.

Main Results:

• A 34-nucleotide sequence (nt 14653-14686) within ORF7 was identified as essential for PRRSV RNA replication.
• This region is critical for the synthesis of negative-strand genomic RNA.
• The essential sequence forms a conserved hairpin structure involved in a 'kissing interaction' with the 3' noncoding region.
• Mutational analysis confirmed the necessity of this kissing interaction for viral replication.

Conclusions:

• The identified 34-nucleotide element in ORF7 is a key cis-acting replication element for PRRSV.
• A novel RNA-RNA interaction mechanism, termed 'kissing interaction', is essential for PRRSV genome replication.
• This finding provides new insights into the molecular mechanisms of PRRSV RNA synthesis and potential targets for antiviral development.