Rho-dependent transcription termination: a revisionist view

Transcription. 2021 Aug;12(4):171-181. doi: 10.1080/21541264.2021.1991773. Epub 2021 Oct 27.


Rho is a hexameric bacterial RNA helicase, which became a paradigm of factor-dependent transcription termination. The broadly accepted ("textbook") model posits a series of steps, wherein Rho first binds C-rich Rho utilization (rut) sites on nascent RNA, uses its ATP-dependent translocase activity to catch up with RNA polymerase (RNAP), and either pulls the transcript from the elongation complex or pushes RNAP forward, thus terminating transcription. However, this appealingly simple mechano-chemical model lacks a biological realism and is increasingly at odds with genetic and biochemical data. Here, we summarize recent structural and biochemical studies that have advanced our understanding of molecular details of RNA recognition, termination signaling, and RNAP inactivation in Rho-dependent transcription termination, rebalancing the view in favor of an alternative "allosteric" mechanism. In the revised model, Rho binds RNAP early in elongation assisted by the cofactors NusA and NusG, forming a pre-termination complex (PTC). The formation of PTC allows Rho to continuously sample nascent transcripts for a termination signal, which subsequently traps the elongation complex in an inactive state prior to its dissociation.

Keywords: RNA polymerase; Rho-dependent termination.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • DNA-Directed RNA Polymerases / metabolism
  • Escherichia coli / genetics
  • Escherichia coli Proteins* / genetics
  • Peptide Elongation Factors / genetics
  • Peptide Elongation Factors / metabolism
  • RNA, Bacterial / chemistry
  • RNA, Bacterial / genetics
  • RNA, Bacterial / metabolism
  • Rho Factor* / genetics
  • Rho Factor* / metabolism
  • Transcription Factors / metabolism
  • Transcription, Genetic
  • Transcriptional Elongation Factors / metabolism


  • Escherichia coli Proteins
  • NusG protein, E coli
  • Peptide Elongation Factors
  • RNA, Bacterial
  • Rho Factor
  • Transcription Factors
  • Transcriptional Elongation Factors
  • nusA protein, E coli
  • DNA-Directed RNA Polymerases