Positive-strand RNA viruses-a Keystone Symposia report.

Positive-strand RNA viruses have been the cause of several recent outbreaks and epidemics, including the Zika virus epidemic in 2015, the SARS outbreak in 2003, and the ongoing SARS-CoV-2 pandemic. On June 18-22, 2022, researchers focusing on positive-strand RNA viruses met for the Keystone Symposium "Positive-Strand RNA Viruses" to share the latest research in molecular and cell biology, virology, immunology, vaccinology, and antiviral drug development. This report presents concise summaries of the scientific discussions at the symposium.

Abracadabra, One Becomes Two: The Importance of Context in Viral -1 Programmed Ribosomal Frameshifting.

The constrained nature of viral genomes has allowed a translational sleight of hand known as -1 Programmed Ribosomal Frameshifting (-1 PRF) to flourish. Numerous studies have sought to tease apart the mechanisms and implications of -1PRF utilizing a few techniques. The dual-luciferase assay and ribosomal profiling have driven the PRF field to make great advances; however, the use of these assays means that the full impact of the genomic and cellular context on -1 PRF is often lost. Here, we discuss how the Minimal Frameshifting Element (MFE) and its constraints can hide contextual effects on -1 PRF. We review how sequence elements proximal to the traditionally defined MFE, such as the coronavirus attenuator sequence, can affect the observed rates of -1 PRF. Further, the MFE-based approach fully obscured -1 PRF in Barley yellow dwarf virus and would render the exploration of -1 PRF difficult in Porcine reproductive and respiratory syndrome virus, Encephalomyocarditis virus, Theiler's murine encephalomyelitis virus, and Sindbis virus. Finally, we examine how the cellular context of tRNA abundance, miRNAs, and immune response elements can affect -1 PRF. The use of MFE was instrumental in establishing the basic foundations of PRF; however, it has become clear that the contextual impact on -1 PRF is no longer the exception so much as it is the rule and argues for new approaches to study -1PRF that embrace context. We therefore urge our field to expand the strategies and methods used to explore -1 PRF.