Figure 6.

Location and distribution of alternative smORFs. (A) Canonical monocistronic mRNA paradigm comprising a unique large CDS between untranslated regions (UTRs). (B) Alternative smORF division and distribution within an mRNA. Upstream smORFs are located in the 5′UTR, and their stop codons may extend across the reference CDS region. The start codons of overlapping smORFs strictly overlap with the reference CDS region, but their sequences may extend to the 3′UTR. Downstream smORFs are located totally within the 3′UTR. (C) Examples of well-known representative mRNAs exhibiting several alternative smORFs (sequence analysis by the authors). Alternative smORFs are commonly encountered in mRNAs, and their coding potential is still underappreciated. Yellow tracks represent reference CDSs (large ORFs); blue tracks represent alternative smORFs.