Rho-dependent transcription termination: mechanisms and roles in bacterial fitness and adaptation to environmental changes

Regulation of RDTT by blocking of the Rut site. (A) Translation–transcription coupling protects intragenic Rut sites from Rho action. (B) Binding of a sRNA to the mRNA leader at/near the RBS prevents translation and unmasks intragenic Rut site(s) leading to RDTT. (C) Restructuring of the mRNA leader upon ligand binding to its cognate riboswitch masks the RBS, allowing RDTT from intragenic Rut sites. Inhibition of RDTT may also stem from sequestering of the Rut site in (D) a secondary RNA structure, or (E) a sRNA–mRNA duplex, or (F) from blocking of the Rut site by a RNA-binding protein (hypothetical case not discussed in main text).