Figure 1.

Key Figure. Localisation of Premature and Full-Length Transcription Termination.

We classify any transcription termination events occurring within the 3′-untranslated region (UTR) of the full-length transcript or downstream of the annotated 3′-UTR, as full-length, whereas those occurring before as premature. Premature transcription termination (PTT) can occur in the vicinity of the transcription start site (TSS), where we call it TSS-linked PTT, or further downstream in the gene body, described here as intragenic PTT. As a rule of thumb, we annotate TSS-linked PTT as corresponding to termination events within the first exon; however, please note that this is not an absolute distinction and is likely to vary on a gene-by-gene basis. PTT can generate unstable (dotted wavy line) or stable (solid wavy line), polyadenylated transcripts. If PTT generates a stable, polyadenylated transcript, it can be classified as alternative polyadenylation (APA) or intronic polyadenylation (IPA). Abbreviation: (A)_n, polyadenylation.