Multiple factors regulate the transcription process by modulating the template switch frequency during discontinuous transcription. The most important one is the complementarity between the TRS-L and the cTRS-B. In a study of several coronaviruses, most sgmRNAs synthesized could be predicted in silico by local base-pairing calculations. Additional factors may regulate sgmRNA levels, such as TRS secondary structure, proximity to the 3′ end, and RNA-RNA or protein-RNA interactions. In this sense, coronavirus N protein has RNA chaperone activity that drives template switching in vitro and may also facilitate template switching during coronavirus transcription. Although nonessential for RNA synthesis, coronavirus nsp1 is associated with viral components of the replication-transcription complex (RTC). Therefore, it may modulate coronavirus RNA synthesis similarly to arterivirus nsp1 protein, which modulates the relative abundance of sgmRNAs and gRNA.