A simple polypyrimidine repeat acts as an artificial Rho-dependent terminator in vivo and in vitro.

In this paper, we present evidence that an efficient Rho-dependent terminator can be created by introducing a simple (AG/TC) n DNA repeat into a transcription unit. The Rho termination activity in vivo and in vitro is dependent on the length and the orientation of the insert. The transcription of at least 30 bp of the (AG/TC) n repeat in the orientation encoding the (rUrC) n sequence on the transcript leads to Rho-dependent termination at a downstream non-terminator site. Our results indicate that the high efficiency of this artificial Rho-dependent terminator is due to optimal interactions between the (rUrC) n RNA sequence and Rho protein. Thus, our findings strongly suggest that an adequate loading site is the primary determinant for Rho termination activity and provide a more defined system for future investigations.