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Transcriptional and Translational Landscape of Equine Torovirus.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Stewart, Hazel 
Brown, Katherine 
Dinan, Adam M 
Irigoyen, Nerea 
Snijder, Eric J 

Abstract

The genus Torovirus (subfamily Torovirinae, family Coronaviridae, order Nidovirales) encompasses a range of species that infect domestic ungulates, including cattle, sheep, goats, pigs, and horses, causing an acute self-limiting gastroenteritis. Using the prototype species equine torovirus (EToV), we performed parallel RNA sequencing (RNA-seq) and ribosome profiling (Ribo-seq) to analyze the relative expression levels of the known torovirus proteins and transcripts, chimeric sequences produced via discontinuous RNA synthesis (a characteristic of the nidovirus replication cycle), and changes in host transcription and translation as a result of EToV infection. RNA sequencing confirmed that EToV utilizes a unique combination of discontinuous and nondiscontinuous RNA synthesis to produce its subgenomic RNAs (sgRNAs); indeed, we identified transcripts arising from both mechanisms that would result in sgRNAs encoding the nucleocapsid. Our ribosome profiling analysis revealed that ribosomes efficiently translate two novel CUG-initiated open reading frames (ORFs), located within the so-called 5' untranslated region. We have termed the resulting proteins U1 and U2. Comparative genomic analysis confirmed that these ORFs are conserved across all available torovirus sequences, and the inferred amino acid sequences are subject to purifying selection, indicating that U1 and U2 are functionally relevant. This study provides the first high-resolution analysis of transcription and translation in this neglected group of livestock pathogens.IMPORTANCE Toroviruses infect cattle, goats, pigs, and horses worldwide and can cause gastrointestinal disease. There is no treatment or vaccine, and their ability to spill over into humans has not been assessed. These viruses are related to important human pathogens, including severe acute respiratory syndrome (SARS) coronavirus, and they share some common features; however, the mechanism that they use to produce sgRNA molecules differs. Here, we performed deep sequencing to determine how equine torovirus produces sgRNAs. In doing so, we also identified two previously unknown open reading frames "hidden" within the genome. Together these results highlight the similarities and differences between this domestic animal virus and related pathogens of humans and livestock.

Description

Keywords

coronavirus, nidovirus, ribosomes, transcription, veterinary pathogens, Animals, Cells, Cultured, Gene Expression Profiling, Horses, Host-Pathogen Interactions, Protein Biosynthesis, Sequence Analysis, RNA, Torovirus, Transcription, Genetic, Viral Proteins, Virus Cultivation

Journal Title

J Virol

Conference Name

Journal ISSN

0022-538X
1098-5514

Volume Title

92

Publisher

American Society for Microbiology
Sponsorship
Wellcome Trust (106207/Z/14/Z)
European Research Council (646891)