Coronavirus sub-genomic mRNA (sgmRNA) synthesis occurs via a process of discontinuous transcription involving complementary transcription regulatory sequences (TRSs), one (TRS-L) encompassing the leader sequence of the 5′ untranslated region (UTR), and the other upstream of each structural and accessory gene (TRS-B). Several coronaviruses have an ORF located between the N gene and the 3′-UTR, an area previously thought to be non-coding in the Gammacoronavirus infectious bronchitis virus (IBV) due to a lack of a canonical TRS-B. Here, we identify a non-canonical TRS-B allowing for a novel sgmRNA relating to this ORF to be produced in several strains of IBV: Beaudette, CR88, H120, D1466, Italy-02 and QX. Interestingly, the potential protein produced by this ORF is prematurely truncated in the Beaudette strain. A single nucleotide deletion was made in the Beaudette strain allowing for the generation of a recombinant IBV (rIBV) that had the potential to express a full-length protein. Assessment of this rIBV in vitro demonstrated that restoration of the full-length potential protein had no effect on viral replication. Further assessment of the Beaudette-derived RNA identified a second non-canonically transcribed sgmRNA located within gene 2. Deep sequencing analysis of allantoic fluid from Beaudette-infected embryonated eggs confirmed the presence of both the newly identified non-canonically transcribed sgmRNAs and highlighted the potential for further yet unidentified sgmRNAs. This HiSeq data, alongside the confirmation of non-canonically transcribed sgmRNAs, indicates the potential of the coronavirus genome to encode a larger repertoire of genes than has currently been identified.
【저자키워드】 coronavirus, Transcription, RNA synthesis, IBV, sub-genomic mRNA, 【초록키워드】 coronavirus, Genome, in vitro, RNA, Protein, viral replication, mRNA, leader sequence, accessory gene, N gene, assessment, discontinuous transcription, UTR, single nucleotide, sgmRNA, strain, complementary, Infectious Bronchitis Virus, TRS-B, TRS-L, Express, Sequencing analysis, full-length, upstream, 3′-UTR, sgmRNAs, deep, TRSs, transcription regulatory sequence, full-length protein, thought, produced, identify, lack, ORF, indicate, occur, demonstrated, transcribed, had no, canonical, 【제목키워드】 Infectious Bronchitis Virus, avian coronavirus, Multiple, produced, transcribed,