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RNase E resolves toxic condensates by counteracting phase separation of Type II RhlB helicases

Published inNucleic acids research, vol. 54, no. 15, gkag801
Publication date2026-08-10
First online date2026-08-12
Abstract

In many Proteobacteria, the RNA helicase RhlB is a component of the RNA degradosome, a multi-protein complex involved in RNA processing and degradation. Within this complex, RhlB interacts with the scaffold endoribonuclease RNase E. In Escherichia coli, allosteric activation of RhlB by RNase E has defined the current paradigm for RhlB regulation. Here, we identify a distinct clade of RhlB helicases, exemplified by Pseudomonas aeruginosa RhlB, which we designate Type II. Unlike Type I RhlB, Type II RhlB helicases contain an N-terminal intrinsically disordered region that drives RNA-dependent liquid-liquid phase separation and enhances RhlB activity. Biochemical, structural, and functional analyses show that P. aeruginosa RNase E binds RhlB through an interface distinct from that described in the E. coli model and, rather than stimulating activity, antagonizes RhlB phase separation. Excessive RhlB condensation impairs bacterial growth at low temperature, and RNase E-mediated control of RhlB condensation maintains growth under these conditions. Together, these findings reveal that conserved RNA degradosome components can engage in distinct regulatory interactions across species and identify condensate dissolution as a novel mechanism regulating RNA helicase activity.

Keywords
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Endoribonucleases / chemistry
  • Endoribonucleases / genetics
  • Endoribonucleases / metabolism
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Models, Molecular
  • Multienzyme Complexes
  • Phase Separation
  • Polyribonucleotide Nucleotidyltransferase
  • Protein Binding
  • Pseudomonas aeruginosa / enzymology
  • Pseudomonas aeruginosa / genetics
  • RNA Helicases / chemistry
  • RNA Helicases / genetics
  • RNA Helicases / metabolism
Citation (ISO format)
HAUSMANN, Stéphane et al. RNase E resolves toxic condensates by counteracting phase separation of Type II RhlB helicases. In: Nucleic acids research, 2026, vol. 54, n° 15, p. gkag801. doi: 10.1093/nar/gkag801
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Identifiers
Journal ISSN0305-1048
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