A conserved opal termination codon optimizes a temperature-dependent trade-off between protein production and...

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Mosquito-transmitted alphaviruses often possess an opal termination codon upstream of viral polymerase.
• This codon plays a crucial role in viral replication and protein processing.

Purpose of the Study:

• To investigate the role of the opal codon in Sindbis virus (SINV) replication across different temperatures.
• To understand how temperature-dependent translational readthrough affects viral fitness and polyprotein processing.

Main Methods:

• Comparative analysis of opal codon performance versus other stop and sense codons in primate and mosquito cells at 37°C and 28°C.
• Investigation of a naturally occurring SINV mutation's effect on sense-codon fitness and viral genomic RNA (gRNA) production.

Main Results:

• The opal codon demonstrates optimal translational readthrough in primate cells at 37°C, outperforming other stop codons.
• Increased readthrough at 28°C reduces opal codon preference in both primate and mosquito cells.
• Opal codons outperform sense codons at 37°C by preventing excess polyprotein production and ensuring proper gRNA synthesis.
• A SINV mutation was found to restore sense-codon fitness at lower temperatures by delaying polyprotein processing for adequate gRNA production.

Conclusions:

• Dual-host alphaviruses employ sophisticated, temperature-dependent strategies involving single codons to optimize replication in diverse environments.
• The opal codon's efficiency is finely tuned to temperature, highlighting a complex interplay between translation and viral fitness.