Structural basis of the transcription termination factor Rho engagement with transcribing RNA polymerase from Thermus thermophilus

Transcription termination is an essential step in transcription by RNA polymerase (RNAP) and crucial for gene regulation. For many bacterial genes, transcription termination is mediated by the adenosine triphosphate-de-pendent RNA translocase/helicase Rho, which causes RNA/DNA dissociation from the RNAP elongation complex (EC). However, the structural basis of the interplay between Rho and RNAP remains obscure. Here, we report the cryo-electron microscopy structure of the Thermus thermophilus RNAP EC engaged with Rho. The Rho hexamer binds RNAP through the carboxyl-terminal domains, which surround the RNA exit site of RNAP, directing the nascent RNA seamlessly from the RNA exit to its central channel. The beta-flap tip at the RNA exit is critical for the Rho-dependent RNA release, and its deletion causes an alternative Rho-RNAP binding mode, which is irrelevant to termination. The Rho binding site overlaps with the binding sites of other macromolecules, such as ribo-somes, providing a general basis of gene regulation.

Automated summary

Transcription termination is an essential step in gene regulation, and is mediated by the RNA translocase/helicase Rho in bacteria. The cryo-electron microscopy structure of the Thermus thermophilus RNA polymerase elongation complex (EC) bound to Rho reveals the binding sites and interactions between Rho and RNA polymerase. The study also suggests a general basis for gene regulation, as the Rho binding site overlaps with other macromolecule binding sites.