Biology subjects

Guerin, J.

Publications and source records attributed to Guerin, J..

5 recordsLinked to original sources

bioRxiv2026

Plasmid-encoded host reprogramming promotes plasmid dissemination

Conjugative plasmids are major drivers of antibiotic resistance dissemination, yet how newly transferred plasmids establish in recipient cells remains poorly understood. Here we investigate YfjB, a previously uncharacterized conserved leading-region protein, which is zygotically induced immediately after plasmid entry and acts specifically during the earliest post-transfer stages. Multi-omics analyses reveal that YfjB reprograms host transcription, triggering extensive metabolic rewiring that compensates the transient fitness cost of plasmid acquisition. Structural analyses show that YfjB is a ParB-like protein containing a CTP-binding domain and a helix-turn-helix DNA-binding motif, linked to a previously uncharacterized dimerization module that forms a V-shaped clamp-like architecture compatible with DNA loading. Consistently, live-cell imaging reveals nucleoid-associated foci in transconjugants, and ChIP-seq identifies multiple chromosomal binding sites. We therefore rename the protein HerB (Host Expression Reprogrammer, ParB-like). More broadly, our findings reveal how mobile genetic elements facilitate their dissemination by transiently subverting host physiology.

microbiology↗

bioRxiv2024

FIGL1 attenuates meiotic interhomolog repair and is counteracted by RAD51 paralog XRCC2 and chromosome axis protein ASY1 during meiosis

Two recombinases, RAD51 and DMC1, catalyze meiotic break repair to ensure crossovers (COs) between homologous chromosomes (interhomolog) rather than between sisters (intersister). FIDGETIN-LIKE-1 (FIGL1) downregulates both recombinases. However, the understanding of FIGL1 functions in meiotic repair remains limited. Here, we discover new genetic interactions of Arabidopsis thaliana FIGL1 that are important in vivo determinants of meiotic repair outcome. In figl1, compromising the RAD51-dependent repair by either losing RAD51 paralogs (RAD51B or XRCC2) or RAD54 or inhibiting RAD51s catalytic activity results in either unrepaired breaks or meiotic CO defects. Further, XRCC2 physically interacts with FIGL1 and partially counteracts FIGL1 for RAD51 focus formation. Our data support that RAD51-mediated repair mechanisms compensate for the FIGL1 dysfunction. FIGL1 is dispensable for intersister repair in dmc1 but is essential for meiotic repair completion in mutants with impaired DMC1 functions and interhomolog bias such as asy1. We show that FIGL1 attenuates interhomolog repair, and ASY1 counteracts FIGL1 to promote interhomolog recombination.

plant biology↗

bioRxiv2023

Rapid meiotic prophase chromosome movements in Arabidopsis thaliana are linked to essential reorganization at the nuclear envelope

Meiotic rapid prophase chromosome movements (RPMs) require connections between the chromosomes and the cytoskeleton, involving SUN (Sad1/UNC-84)-domain-containing proteins at the inner nuclear envelope (NE). RPMs remain significantly understudied in plants, notably with respect to their importance in the regulation of meiosis. Here, we demonstrate that Arabidopsis thaliana meiotic centromeres undergo rapid (up to 500 nm/s) and uncoordinated movements during the zygotene and pachytene stages. RPMs are not affected by altered chromosome organization and recombination but are abolished in the double mutant sun1 sun2. We also document the changes in chromosome dynamics and nucleus organization during the transition from leptotene to zygotene, including telomere attachment to SUN-enriched NE domains, bouquet formation, and nucleolus displacement, all of which were defective in sun1 sun2. These results establish A. thaliana as a new model species for studying the functional implications of meiotic RPMs and demonstrate the mechanistic conservation of telomere-led RPMs in plants.

genetics↗

bioRxiv2022

Designed Ankyrin Repeat Proteins provide insights into the structure and function of CagI and are potent inhibitors of CagA translocation by the Helicobacter pylori type IV secretion system

The bacterial human pathogen Helicobacter pylori produces a type IV secretion system (cagT4SS) to inject the oncoprotein CagA into gastric cells. The cagT4SS external pilus mediates attachment of the apparatus to the target cell and the delivery of CagA. While the composition of the pilus is unclear, CagI is present at the surface of the bacterium and required for pilus formation. Here, we have investigated the properties of CagI by an integrative structural biology approach. Using Alpha Fold 2 and Small Angle X-ray scattering, it was found that CagI forms elongated dimers mediated by rod-shaped N-terminal domains (CagIN) and prolonged by globular C-terminal domains (CagIC). Three Designed Ankyrin Repeat Proteins (DARPins) K2, K5 and K8 selected against CagI interacted with CagIC with subnanomolar affinities. The crystal structures of the CagI:K2 and CagI:K5 complexes were solved and identified the interfaces between the molecules, thereby providing a structural explanation for the difference in affinity between the two binders. Purified CagI and CagIC were found to interact with adenocarcinoma gastric (AGS) cells, induced cell spreading and the interaction was inhibited by K2. The same DARPin inhibited CagA translocation by up to 65% in AGS cells while inhibition levels were 40% and 30% with K8 and K5, respectively. Our study suggests that CagIC plays a key role in cagT4SS-mediated CagA translocation and that DARPins targeting CagI represent potent inhibitors of the cagT4SS, a crucial risk factor for gastric cancer development. Author summaryHelicobacter pylori is a bacterial pathogen that colonises the human stomach in half of the worlds population. The most virulent strains use the cag- type IV secretion system (cagT4SS), a molecular nanomachine capable of injecting the oncoprotein CagA into gastric cells. How CagA is delivered is unknown, but the cagT4SS produces an external appendage referred to as pilus, which interacts with host cell receptors, mediating CagA translocation from the cytoplasm of the bacteria to the inner membrane of the host cell. In this study we have investigated the structural and functional properties of CagI, a protein long-thought to be associated with the cagT4SS pilus but with yet unknown function. We found that CagI displays a unique dimeric structure and that its C-terminal domain is involved in interaction with the host cell. Designed Ankyrin Repeat Proteins were selected against CagI and found to interact with its C-terminal moiety with high affinity. DARPin binding was able to prevent CagI interaction with the host cell and inhibited CagA translocation by H. pylori. Our study reveals the role of CagI in cagT4SS interaction with gastric cells and provides a first example of a small protein binder inhibiting the cagT4SS activity.

microbiology↗

bioRxiv2021

Large-scale conformational changes of FhaC provide insights into the two-partner secretion mechanism

The Two-Partner secretion pathway mediates protein transport across the outer membrane of Gram-negative bacteria. TpsB transporters belong to the Omp85 superfamily, whose members catalyze protein insertion into, or translocation across membranes without external energy sources. They are composed of a transmembrane {beta} barrel preceded by two periplasmic POTRA domains that bind the incoming protein substrate. Here we used an integrative approach combining in vivo assays, mass spectrometry, nuclear magnetic resonance and electron paramagnetic resonance techniques suitable to detect minor states in heterogeneous populations, to explore transient conformers of the TpsB transporter FhaC. This revealed substantial, spontaneous conformational changes with a portion of the POTRA2 domain coming close to the lipid bilayer and surface loops. Specifically, the amphipathic {beta} hairpin immediately preceding the first barrel strand can insert into the {beta} barrel. We propose that these motions enlarge the channel and hoist the substrate into it for secretion. An anchor region at the interface of the {beta} barrel and the POTRA2 domain stabilizes the transporter in the course of secretion. Our data propose a solution to the conundrum how these transporters mediate protein secretion without the need for cofactors, by utilizing intrinsic protein dynamics.

biophysics↗