Intrinsic and Rho-dependent termination cooperate for efficient transcription termination at 3' untranslated regions

Abstract

The intrinsic, and the Rho-dependent mechanisms of transcription termination are conserved in bacteria. Generally, the two mechanisms have been illustrated as two independent pathways occurring in the 3 ends of different genes with contrasting requirements to halt RNA synthesis. However, a majority of the intrinsic terminators terminate transcription inefficiently leading to transcriptional read-through. The unwanted transcription in the downstream region beyond the terminator would have undesired consequences. To prevent such transcriptional read-through, bacteria must have evolved ways to terminate transcription more efficiently at or near the termination sites. We describe the participation of both the mechanisms, where intrinsic terminator and Rho factor contribute to prevent transcriptional read-through. Contribution from both the termination processes is demonstrated at the downstream regions of the genes both in vitro and in vivo in mycobacteria. Distinct patterns of cooperation between the two modes of termination were observed at the 3 untranslated regions of the genes to ensure efficient termination. We demonstrate similar mode of operation between the two termination processes in Escherichia coli suggesting a likely prevalence of this cooperation across bacteria. The reporter system developed to assess the Rho - intrinsic termination collaboration in vivo for mycobacteria and E. coli can readily be applied to other bacteria.