Novel classes of replication-associated transcripts discovered in viruses.

The role of RNA molecules in the priming of DNA replication and in providing a template for telomerase extension has been known for decades. Since then, several transcripts have been discovered, which play diverse roles in governing replication, including regulation of RNA primer formation, the recruitment of replication origin (Ori) recognition complex, and the assembly of replication fork. Recent studies on viral transcriptomes have revealed novel classes of replication-associated (ra)RNAs, which are expressed from the genomic locations in close vicinity to the Ori. Many of them overlap the Ori, whereas others are terminated close to the replication origin. These novel transcripts can be both protein-coding and non-coding RNAs. The Ori-overlapping part of the mRNAs is generally either the 5'-untranslated regions (UTRs), or the 3'-UTRs of the longer isoforms. Several raRNAs have been identified in various viral families using primarily third-generation long-read sequencing. Hyper-editing of these transcripts has also been described.