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Continuous and discontinuous RNA synthesis in coronaviruses part 13

  RNA sequences regulating transcription The transcription process is controlled by transcription-regulating sequences (TRSs) located at the 3′ end of the leader sequence (TRS-L) and preceding each viral gene (TRS-B). TRSs include a conserved core sequence (CS) 6-7 nt in … Continue reading

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Continuous and discontinuous RNA synthesis in coronaviruses part 12

  Moreover, as noted below, the complement of the leader sequence supports initiation of positive-strand RNA synthesis, making the negative-strand subgenomic RNAs (sgRNAs) a template for further amplification of positive-strand sgmRNAs.

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Continuous and discontinuous RNA synthesis in coronaviruses part 11

  The observation raises the question of whether the presence of the leader sequence in coronavirus sgmRNAs provides any selective advantage to the virus. The presence of the 5′ leader sequence was shown to protect SARS-CoV mRNAs from nsp1-induced endonucleolytic … Continue reading

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Continuous and discontinuous RNA synthesis in coronaviruses part 10

  The transcription mechanismin coronaviruses is seemingly complicated as compared with the transcription mechanisms in other positive-strand RNA viruses, such as internal initiation and premature termination. In fact, in contrast to coronavirus and arterivirus sgmRNAs, subgenomic transcripts of other Nidovirales, … Continue reading

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Continuous and discontinuous RNA synthesis in coronaviruses part 9

  In contrast to replication, coronavirus transcription includes a discontinuous step during the production of sgmRNA. This process, unique among known RNA viruses, is a hallmark of the order Nidovirales and ultimately generates a nested set of sgmRNAs that are … Continue reading

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Continuous and discontinuous RNA synthesis in coronaviruses part 8

  Like that of other positive-strand RNA viruses, coronavirus genome replication is a process of continuous synthesis that utilizes a full-length complementary negative-strand RNA as the template for the production of progeny virus genomes. The initiationĀ  of negative-strand synthesis involves … Continue reading

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Continuous and discontinuous RNA synthesis in coronaviruses part 7

  Coronavirus RNA-dependent RNA synthesis includes two differentiated processes: genome replication, yielding multiple copies of genomic RNA (gRNA), and transcription of a collection of sgmRNAs that encode the viral structural and accessories proteins.

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Continuous and discontinuous RNA synthesis in coronaviruses part 6

  The 5′-proximal two-thirds of the coronavirus genome encodes the replicase gene, which contains two open reading frames, ORF1a and ORF1b. Translation of ORF1a yields polyprotein 1a (pp1a), andĀ  -1 ribosomal frameshifting allows translation of ORF1b to yield pp1ab. Together, … Continue reading

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Continuous and discontinuous RNA synthesis in coronaviruses part 5

  Two recent HCoVs, severe acute respiratory syndrome coronaviruses (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), emerged in 2002 and 2012, respectively, causing life-threathening diseaseĀ  in humans. In addition, novel animal coronaviruses, such as the porcine deltacoronavirus (PDCoV) and … Continue reading

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Continuous and discontinuous RNA synthesis in coronaviruses part 4

  Coronaviruses are enveloped, positive-strand RNA viruses with genomes approximately 30 kb in length that belong to the family Coronaviridae in the order Nidovirales. Coronaviruses infect a wide variety of mammalian and avian species, in most cases causing respiratory and … Continue reading

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