The nucleocapsid protein gene of bovine coronavirus is bicistronic

Abstract

For animal RNA viruses that replicate through an RNA intermediate, reported examples of bicistronic mRNAs with overlapping open reading frames in which one cistron is contained entirely within another have been made only for those with negative-strand or double-stranded genomes. In this report, we demonstrate for the positive-strand bovine coronavirus that an overlapping open reading frame potentially encoding a 23-kDa protein (names the I [for internal open reading frame] protein) and lying entirely within the gene for the 49-kDa nucleocapsid phosphoprotein is expressed during virus replication from a single species of unedited mRNA. The I protein was specifically immunoprecipitated from virus-infected cells with an I-specific antipeptide serum and was shown to be membrane associated. Many features of I protein synthesis conform to the leaky ribosomal scanning model for regulation of translation. This, to our knowledge, is the first example of a bicistronic mRNA for a cytoplasmically replicating, positive-strand animal RNA virus in which one cistron entirely overlaps another.

Isolation and sequence analysis of canine respiratory coronavirus

“…The CRCoV N protein was found to be highly similar to that of other group 2 coronaviruses. The nucleocapsid protein gene contained an internal ORF coding for a protein with high similarity to the BCoV I protein (Senanayake et al, 1992). An I protein homologue is also present in MHV (Fischer et al, 1997), CoV HKU-1 (Woo et al, 2005), HEV and HCoV-OC43 but not in other coronavirus groups.…”

Viral and Cellular mRNA Translation in Coronavirus-Infected Cells

“…The first AUG has a suboptimal Kozak context, while the downstream AUG (the start codon for the I protein) is in a more favorable Kozak context (Senanayake and Brian, 1997;Senanayake et al, 1992). The N genes of MHV-A59, HCoV-HKU1, HCoV-OC43, SARS-CoV, and MERS-CoV also have an internal ORF (Armstrong et al, 1983;Kamahora et al, 1989;Rota et al, 2003;van Boheemen et al, 2012;Woo et al, 2005); in HCoV-OC43, the AUG start codon of the internal ORF is changed to AUC.…”

Molecular Interactions in the Assembly of Coronaviruses

“…These so-called group-specific genes appear not to be essential as shown by the occurrence of natural mutants defective in some of them (Brown and Brierley, 1995;Herrewegh et al, 1995;Kennedy et al, 2001;Luytjes, 1995;Shen et al, 2003;Vennema, 1999;Vennema et al, 1998;Woods, 2001) and by the observed viability of engineered deletion mutants lacking some or all of these genes (de Haan et al, 2002b;Fischer et al, 1997;Haijema et al, 2004;Ortego et al, 2003;Sola et al, 2001). Except for the group 2-specific HE protein and, possibly, the poorly characterized I protein (Fischer et al, 1997;Senanayake et al, 1992), the latter encoded by an open reading frame completely contained within the N gene, the group- The single-stranded, positive-sense RNA genome contains 5 0 -and 3 0 -terminal untranslated regions (UTRs) with a 5 0 -terminal cap and a 3 0 -terminal poly(A) tract. The leader sequence (L) in the 5 0 UTR is indicated.…”