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A large insertion domain in the Rho factor from a low G+C, Gram-negative bacterium is critical for RNA binding and transcription termination activity

Abstract : Rho-dependent termination of transcription (RDTT) is a critical regulatory mechanism specific to bacteria. In a subset of species including most Actinobacteria and Bacteroidetes, the Rho factor contains a large, poorly conserved N-terminal insertion domain (NID) of cryptic function. To date, only two NID-bearing Rho factors from high G+C Actinobacteria have been thoroughly characterized. Both can trigger RDTT at promoter-proximal sites or with structurally constrained transcripts that are unsuitable for the archetypal, NID-less Rho factor of Escherichia coli (EcRho). Here, we provide the first biochemical characterization of a NID-bearing Rho factor from a low G+C bacterium. We show that Bacteroides fragilis Rho (BfRho) is a bona fide RNA-dependent NTPase motor able to unwind long RNA:DNA duplexes and to disrupt transcription complexes. The large NID (~40% of total mass) strongly increases BfRho affinity for RNA, is strictly required for RDTT, but does not promote RDTT at promoter-proximal sites or with a structurally constrained transcript. Furthermore, the NID does not preclude modulation of RDTT by transcription factors NusA and NusG or by the Rho inhibitor bicyclomycin. Although the NID contains a prion-like Q/N-rich motif, it does not spontaneously trigger formation of -amyloids. Thus, despite its unusually large RNA binding domain, BfRho behaves more like the NID-less EcRho than NID-bearing counterparts from high G+C Actinobacteria. Our data highlight the evolutionary plasticity of Rho's N-terminal region and illustrate how RDTT is adapted to distinct genomic contents.
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https://hal-cnrs.archives-ouvertes.fr/hal-03248336
Contributor : Marc Boudvillain Connect in order to contact the contributor
Submitted on : Thursday, June 3, 2021 - 3:13:46 PM
Last modification on : Tuesday, October 12, 2021 - 5:20:22 PM
Long-term archiving on: : Saturday, September 4, 2021 - 6:53:18 PM

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Isabelle Simon, Mildred Delaleau, Annie Schwartz, Marc Boudvillain. A large insertion domain in the Rho factor from a low G+C, Gram-negative bacterium is critical for RNA binding and transcription termination activity. Journal of Molecular Biology, Elsevier, 2021, 433 (15), pp.167060. ⟨10.1016/j.jmb.2021.167060⟩. ⟨hal-03248336⟩

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