Equine arteritis virus subgenomic RNA transcription: UV inactivation and translation inhibition studies.

The study explores the expression of genetic information in equine arteritis virus (EAV), particularly focusing on the creation of six subgenomic mRNAs. Using UV transcription mapping and translation inhibition methods, the researchers discovered that the majority of EAV’s sg RNAs are not derived from a genome-length precursor. They also found that ongoing protein synthesis is more essential for the synthesis of sg RNA than genomic RNA.

Explanation of the Research

• This research primarily focuses on the genetic expression of the equine arteritis virus (EAV), which is part of the arterivirus family. The process of its genetic expression involves synthesizing six subgenomic, or sg, mRNAs, which are parts of the RNA composed of a lead and a body sequence. These sequences are identical to the 5′ and 3′ ends of the genome, indicating that both ends of the sequences are the same.
• Early theories suggested that the synthesis may involve cis-splicing of a genome-length precursor RNA. Cis-splicing is a method of RNA processing, which permits one single gene to code for multiple proteins in different cellular situations. This study sought to reassess these suggestions and conducted a comparative analysis using the coronavirus mouse hepatitis virus (MHV), and the alphavirus Sindbis virus.
• UV transcription mapping, a method that uses UV radiation to control gene expression, was implemented for this investigation. Through this process, they noted that the majority of EAV’s sg RNAs made at later stages of the infection did not originate from a genome-length precursor. However, they found that total independence of sg RNA synthesis from the genomic RNA synthesis was never observed during infection.
• The researchers decided to probe further into the effect of UV radiation on the synthesis of the viral replicase, the enzyme that aids in viral replication. This involved application of cycloheximide, an inhibitor of translation in eukaryotic organisms. The results suggested that ongoing protein synthesis was more crucial to the synthesis of sg RNA than the synthesis of genomic RNA for EAV.
• Cycloheximide affected EAV genomic RNA synthesis as it appears to be more dependent on de novo protein synthesis in early infection stages. Meanwhile, MHV’s transcription appeared to be extremely sensitive to translation inhibition. However, over time, EAV’s genomic RNA synthesis became less reliant on de novo protein synthesis.