Biology subjects

Geslain, S. A. M.

Publications and source records attributed to Geslain, S. A. M..

3 recordsLinked to original sources

bioRxiv2026

Intrinsic features of the RNase E membrane targeting sequence specify RNA degradosome organisation and activity

In bacteria, transcription and RNA degradation are physically separated via segregation of the main ribonucleolytic machinery - the RNA degradosome - into phase-separated or membrane-anchored molecular assemblies driven by RNase E. Despite the widespread conservation of an amphipathic membrane anchor (MTS) in RNase E, the regulatory information embedded within this sequence and its biological importance remain poorly understood. Here, we have studied the importance of the Pseudomonas aeruginosa RNase E MTS for bacterial fitness or virulence and assessed its interchangeability. We show that amphipathicity is dispensable for foci scaffolding but necessary for proper foci morphology, dynamics, and localisation, although sequence modulates foci behaviour. Loss of the MTS additionally causes a drastic sensitivity to high salinity and a consistent virulence defect in Galleria mellonella larvae. Moreover, transcriptomics and analysis of mRNA spatial organisation reveal that the MTS mutant has specific stabilisation of localised membrane protein-encoding transcripts, together with abnormal operon processing. Altogether, our study highlights the elegant MTS-mediated control of spatial organisation and target selection, shaping the transcriptome and bacterial stress response.

microbiology↗

bioRxiv2024

Critical functions and key interactions mediated by the RNase E scaffolding domain in Pseudomonas aeruginosa

The RNA degradosome is a bacterial multi-protein complex mediating mRNA processing and degradation. In Pseudomonadota, this complex assembles on the C-terminal domain (CTD) of RNase E through short linear motifs (SLiMs) that determine its composition and functionality. In the human pathogen Pseudomonas aeruginosa, the RNase E CTD exhibits limited similarity to that of model organisms, impeding our understanding of RNA metabolic processes in this bacterium. Our study systematically maps the interactions mediated by the P. aeruginosa RNase E CTD and highlights its critical role in transcript regulation and cellular functions. We identified the SLiMs crucial for membrane attachment, RNA binding and complex clustering, as well as for direct binding to the core components PNPase and RhlB. Transcriptome analyses of RNase E CTD mutants revealed altered expression of genes involved in quorum sensing, type III secretion, and amino acid metabolism. Additionally, we show that the mutants are impaired in cold adaptation, pH response, and virulence in an infection model. Overall, this work establishes the essential role of the RNA degradosome in driving bacterial adaptability and pathogenicity. Author summaryBacteria must rapidly adapt to changing environments, whether facing temperature shifts, nutrient scarcity, or antibiotic exposure. A key mechanism enabling this adaptability is the regulation of mRNA levels--the molecular blueprints for protein production. This process is governed by the RNA degradosome, a multi-protein complex that processes and degrades RNA to control gene expression. Although the RNA degradosome core function is conserved across bacteria, its composition and organization differ significantly between species, reflecting diverse lifestyles and environmental challenges each bacterium encounter. In this study, we investigated the RNA degradosome in Pseudomonas aeruginosa, a bacterial pathogen causing difficult-to-treat infections in humans. We identified its components and mapped regions within the complex essential for RNA binding, membrane attachment, and spatial organization. Disrupting these regions compromised P. aeruginosa ability to survive in cold conditions, respond to stress, and establish an infection. Through this work, we uncovered unique features of the P. aeruginosa RNA degradosome that distinguish it from those of other species, emphasizing the RNA degradosome critical role in bacterial adaptability and highlight it as a promising target for therapies against P. aeruginosa infections.

microbiology↗

bioRxiv2024

Intrinsically disordered regions regulate RhlE RNA helicase functions in bacteria

RNA helicases--central enzymes in RNA metabolism-- often feature intrinsically disordered regions (IDRs) that enable phase separation and complex molecular interactions. In the bacterial pathogen Pseudomonas aeruginosa, the non-redundant RhlE1 and RhlE2 RNA helicases share a conserved REC catalytic core but differ in C-terminal IDRs. Here, we show how the IDR diversity defines RhlE RNA helicase specificity of function. Both IDRs facilitate RNA binding and phase separation, localizing proteins in cytoplasmic clusters. However, RhlE2 IDR is more efficient in enhancing REC core RNA unwinding, exhibits a greater tendency for phase separation, and interacts with the RNase E endonuclease, a crucial player in mRNA degradation. Swapping IDRs results in chimeric proteins that are biochemically active but functionally distinct as compared to their native counterparts. The RECRhlE1-IDRRhlE2 chimera improves cold growth of a rhlE1 mutant, gains interaction with RNase E and affects a subset of both RhlE1 and RhlE2 RNA targets. The RECRhlE2-IDRRhlE1 chimera instead hampers bacterial growth at low temperatures in the absence of RhlE1, with its detrimental effect linked to aberrant RNA droplets. By showing that IDRs modulate both protein core activities and subcellular localization, our study defines the impact of IDR diversity on the functional differentiation of RNA helicases.

molecular biology↗