Cross-genus analysis reveals architecturally programmed sgRNA synthesis patterns in coronaviruses.

Abstract

Coronaviruses employ discontinuous transcription to produce canonical subgenomic RNAs (sgRNAs) essential for gene expression. Although TRS-dependent template switching mechanism has been proposed, its structural basis remains poorly defined, and the functional significance of abundant non-canonical sgRNAs persists as a critical gap since the discovery of discontinuous RNA synthesis. Here, we help bridge this gap through the first cross-genus integrated analysis of coronavirus transcriptomes and RNA interactomes. We show that canonical sgRNA formation is associated with same-direction RNA-RNA interactions. In contrast, non-canonical sgRNAs form through distinct architectural mechanisms: short-range junctions mediated by stem-loop structures overlapping genomic deletion hotspots, and conserved long-range ORF1a-N interactions generating sgRNAs encoding immune-modulatory ORFs - a function not previously attributed to non-canonical transcription. These findings suggest architecturally programmed discontinuous RNA synthesis and highlight a potential link between non-canonical sgRNAs, genomic plasticity, and immune modulation, which may have implications for coronavirus adaptation.