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Figure 5.14 Discontinuous transcriptional model of RNA synthesis. (A, B) Subgenomic RNA (sgRNA) synthesis begins at the 3′ end of
the positive sense genomic RNA template. (C) To monitor the base-pair complementarity of the negative-strand RNA with the TRS-L by a
component of the replicase-transcriptase complex, the genomic template loops out for this purpose. (D) As transcription proceeds towards
the 5′ of the genomic RNA, it encounters a TRS-B and pauses. (E) At this point, the nascent negative strand may choose to bypass the
TRS-B and resume elongation. Alternatively, it may switch templates by binding to TRS-L. (F) If elongation is resumed, this would result in
the complete synthesis of the antileader containing negative-strand sgRNA. (G) These genome and negative-strand sgRNA can then act as
templates for the synthesis of positive-sense sgRNA.

M protein is crucial to ensure it is incorporated into the progeny traditional exocytosis pathway, or if specialized pathway is used
virions. for their exit. This is exemplified in some CoVs, where a pro-
Upon the completion of virion assembly, the virions are portion of S protein which has not yet been assembled into the
transported in vesicles and released by exocytosis. However, it virions would transit to the plasma membrane to mediate fusion
remains to be clearly defined whether the virions exit using the with neighbouring uninfected cells (Godeke et al., 2000). This