Coronavirus transcription model

Experimental data on transcription in coronaviruses and the related arteriviruses can be integrated into a transcription model that includes three steps.

• First, gRNA forms transcription initiation precomplexes, bringing into physical proximity the distal TRS-L and TRS-B. RNA-RNA, RNA-protein, and protein-protein interactions  might maintain these precomplexes in a dynamic equilibrium.
• These precomplexes act as slowdown and detachment signals for the transcription complex during the synthesis of negative-strand RNA
• Once the TRS-B has been copied, if the ΔG of duplex formation between the cTRS-B (in the nascent negative-strand RNA) and the TRS-L exceeds a minimum treshold, a template switch to the leader takes place, adding a copy of the TRS-L exceeds a minimum treshold, a template switch to the leader takes place, adding a copy of the TRS-L to complete the negative-strand sgRNA. These negative-strand sgRNAs subsequently serve as templates for the synthesis of multiple copies of sgmRNAs