Pre-termination Transcription Complex: Structure and Function

Rho is a general transcription termination factor playing essential roles in RNA polymerase (RNAP) recycling, gene regulation, and genomic stability in most bacteria. Traditional models of transcription termination postulate that hexameric Rho loads onto RNA prior to contacting RNAP and then translocates along the transcript in pursuit of the moving RNAP to pull RNA from it. Here, we report the cryoelectron microscopy (cryo-EM) structures of two termination process intermediates. Prior to interacting with RNA, Rho forms a specific pre-termination complex'' (PTC) with RNAP and elongation factors NusA and NusG, which stabilize the PTC. RNA exiting RNAP interacts with NusA before entering the central channel of Rho from the distal C-terminal side of the ring. We map the principal interactions in the PTC and demonstrate their critical role in termination. Our results support a mechanism in which the formation of a persistent PTC is a prerequisite for termination.

Automated summary

Rho is a crucial factor in transcription termination in bacteria, forming a pre-termination complex with RNAP and elongation factors to stabilize the process. RNA interacts with NusA before entering the central channel of Rho, highlighting the critical role of these interactions in termination. The study supports a mechanism where the formation of a persistent pre-termination complex is essential for the termination process.