Cloning and analysis of strong promoters is made possible by the downstream placement of a RNA termination signal.

Abstract
Downstream placement of a strong transcriptional termination signal has made it possible to clone (in Escherichia coli) bacteriophage T5 promoters known to exhibit high signal strength. The cloning system constructed contains 2 easily assayable indicator functions whose expression is controlled by the integration of promoters and terminators, respectively. By assessing transcription within the indicator regions, the efficiency of promoters and termination signals can be determined in vitro and in vivo.