Programmed -2/-1 Ribosomal Frameshifting in Simarteriviruses: an Evolutionarily Conserved Mechanism

Area of Science:

• Virology
• Molecular Biology
• Genomics

Background:

• Porcine reproductive and respiratory syndrome virus (PRRSV) utilizes -2/-1 programmed ribosomal frameshifting (-2/-1 PRF) to produce additional viral proteins.
• This mechanism is crucial for viral replication and involves viral protein nsp1β and cellular poly(rC) binding proteins (PCBPs).
• Simarteriviruses, arteriviruses infecting nonhuman primates, are undercharacterized despite potential zoonotic risks.

Purpose of the Study:

• To investigate the -2/-1 PRF mechanism in simarteriviruses and other arteriviruses.
• To identify key viral and cellular factors involved in simarterivirus -2/-1 PRF.
• To assess the evolutionary conservation and functional significance of -2/-1 PRF in arteriviruses.

Main Methods:

• Comparative genomic sequence analysis of arteriviruses.
• Identification of critical elements for -2/-1 PRF (slippery sequence, C-rich motif).
• In vitro translation assays and reverse genetics in simian hemorrhagic fever virus (SHFV) and infected cells.

Main Results:

• Key elements for -2/-1 PRF were identified in 11 simarteriviruses, with variations affecting frameshift efficiency.
• SHFV nsp1β, particularly Tyr111 and Arg114, is essential for transactivating both -2 and -1 PRF.
• PCBPs are involved in simarterivirus -2/-1 PRF, and impaired nsp2TF/nsp2N expression leads to attenuated SHFV growth.

Conclusions:

• -2/-1 PRF is an evolutionarily conserved mechanism in non-EAV/-WPDV arteriviruses for expressing essential viral proteins.
• This mechanism, involving nsp1β and PCBPs, is critical for viral replication.
• The study highlights a novel, unprecedented frameshifting mechanism in eukaryotic systems, with implications beyond virology.