Figure 1. Schematic representation of how long bacterial 3′-UTRs can be generated.

A transcript ending in a transcriptional terminator located far away from the corresponding protein stop codon generates a bona fide long 3′-UTR. In other cases, despite the presence of a transcriptional terminator (TT) close to the end of the protein stop codon, transcription may continue downstream the predicted TT, generating a terminating-read-through-dependent long 3′-UTR. In addition, several transcripts end at a TT that is part of the expression platform of a riboswitch. In this case the long 3′-UTRs will be generated only when the riboswitch is in an OFF configuration. Otherwise, if the riboswitch is in an ON configuration, a polycistronic transcript is generated.