The Sole DEAD-Box RNA Helicase of the Gastric Pathogen Helicobacter pylori Is Essential for Colonization

Abstract

Present in every kingdom of life, generally in multiple copies, DEAD-box RNA helicases are specialized enzymes that unwind RNA secondary structures. They play major roles in mRNA decay, ribosome biogenesis, and adaptation to cold temperatures. Most bacteria have multiple DEAD-box helicases that present both specialized and partially redundant functions. By using phylogenomics, we revealed that the Helicobacter genus, including the major gastric pathogen H. pylori, is among the exceptions, as it encodes a sole DEAD-box RNA helicase. In H. pylori, this helicase, designated RhpA, forms a minimal RNA degradosome together with the essential RNase, RNase J, a major player in the control of RNA decay. Here, we used H. pylori as a model organism with a sole DEAD-box helicase and investigated the role of this helicase in H. pylori physiology, ribosome assembly, and during in vivo colonization. Our data showed that RhpA is dispensable for growth at 37°C but crucial at 33°C, suggesting an essential role of the helicase in cold adaptation. Moreover, we found that a ΔrhpA mutant was impaired in motility and deficient in colonization of the mouse model. RhpA is involved in the maturation of 16S rRNA at 37°C and is associated with translating ribosomes. At 33°C, RhpA is, in addition, recruited to individual ribosomal subunits. Finally, via its role in the RNA degradosome, RhpA directs the regulation of the expression of its partner, RNase J. RhpA is thus a multifunctional enzyme that, in H. pylori, plays a central role in gene regulation and in the control of virulence.

Pathogenesis of Helicobacter pylori infection

“…This approach may be applied to other virulence factors for understanding their roles under certain conditions, in either in vitro or in vivo studies. Additional initial colonization factors studied included GGT and RhpA, an RNA helicase protein, mutants of which showed colonization attenuation in the animal model . The GGT is an especially important factor in the early colonization by its metabolic activity and then has additional functions as a defensive agent against the host's immune response.…”

“…GGT activity promotes a preferred recruitment of CD8 + T cells over CD4 + T cells, whereas RhpA more likely influences motility of H. pylori and adaptation to colder environments. In addition, RhpA also regulates the expression of RNase J, which may put this protein in the role of central determinant of gene regulation and virulence control …”

“…Additional initial colonization factors studied included GGT and RhpA, an RNA helicase protein, mutants of which showed colonization attenuation in the animal model. 28,29 The GGT is an especially important factor in the early colonization by its metabolic activity and then has additional functions as a defensive agent against the host's immune response. GGT activity promotes a preferred recruitment of CD8 + T cells over CD4 + T cells, 29 whereas RhpA more likely influences motility of H. pylori and adaptation to colder environments.…”

“…In addition, RhpA also regulates the expression of RNase J, which may put this protein in the role of central determinant of gene regulation and virulence control. 28 Flolitin-like protein is described as a membrane raft-associated protein. 30 Protein analysis revealed that FLOT is located in the membrane.…”

The RNase J-Based RNA Degradosome Is Compartmentalized in the Gastric Pathogen Helicobacter pylori

“…In the Gram-negative pathogen Helicobacter pylori , we recently demonstrated the existence of a minimal RNA degradosome composed of two partners ( 11 – 13 ). H. pylori is a spiral-shaped bacterium that persistently colonizes the stomach of more than half of the human population worldwide ( 14 ) and causes chronic gastritis, peptic ulcers, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric carcinoma, which is responsible for 800,000 deaths per year in the world ( 15 , 16 ).…”