Background
The transcription terminator is placed at the 3' end of the target gene. It enhances plasmid stability by preventing transcription through the replication region and through other promoters located on the plasmid.  Continued transcription from strong promoters into the replication region can destabilize plasmids due to overproduction of the ROP protein, which is involved in the control of plasmid copy number. The presence of transcription terminators also prevents formation of antisense RNAs from downstream promoters operating in reverse orientation with respect to the target gene. In addition, the transcription terminator enhances the stability of the mRNA transcript by a stem-loop formation at the 3' end.