Biology subjects

Guittat, L.

Publications and source records attributed to Guittat, L..

3 recordsLinked to original sources

bioRxiv2026

G4All: a database of experimentally confirmed G-quadruplex-forming sequences

G-quadruplexes (G4s) are non-canonical nucleic acid structures with critical roles in gene regulation, genomic stability, and disease, making them prime targets for therapeutic and biotechnological applications. However, the absence of a curated, centralized, experimentally validated repository of short (mostly synthetic) G4-forming sequences, paired with appropriate single-stranded or hairpin controls, has limited reproducibility and hindered progress in the field. Here, we introduce G4All, a comprehensive, curated database of G4-forming short DNA and RNA sequences, complemented by rigorously selected non-G4 controls, all studied under roughly similar experimental conditions (around 100 mM potassium ion at near neutral pH). G4All consolidates sequences validated by diverse experimental methods, including circular dichroism, NMR, UV spectroscopy, with standardized annotations for topology, thermal stability, and experimental conditions. By providing both positive and negative datasets, G4All enables rigorous comparative analyses, assay benchmarking, and the development of predictive models. The database supports a broad range of applications, from fundamental studies of G4 biophysics to the rational design of aptamers, as well as benchmarking prediction algorithms. Future developments will expand G4All to include user-submitted datasets and more RNA sequences. Freely accessible, G4All offers a searchable interface and downloadable datasets, establishing a community-driven hub to accelerate discovery and standardization in G4 research. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/743020v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@111d015org.highwire.dtl.DTLVardef@74447corg.highwire.dtl.DTLVardef@13c5642org.highwire.dtl.DTLVardef@432469_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Lysosomal membrane permeabilization enhances the anticancer effects of RNA Polymerase I transcription inhibitors

Lysosomes are known to contribute to the development of drug resistance through a variety of mechanisms that include the sequestration of drugs within their compartments and the activation of adaptive stress pathways. Although targeting POL I (RNA polymerase I) exhibits anticancer effects, little attention has been paid to the contribution of lysosomes to the efficacy and resistance of RNA POL I inhibitors. In this study, we investigated this aspect in the context of two potent POL I inhibitors, CX-3543 (Quarfloxin) and CX-5461 (Pidnarulex). Unexpectedly, CX-3543 was discovered to be sequestered in the lysosomal compartment. This resulted in the permeabilization of lysosomal membranes (LMP) and the subsequent activation of cellular stress adaptation pathways, including the transcription factor (TFEB) and autophagy. Disruption of TFEB or autophagy increased cell sensitivity to CX-3543, highlighting the cytoprotective role of these processes against cell death induced by this compound. Moreover, targeting lysosomal membranes using chloroquine derivatives or blue light excitation induced substantial LMP, resulting in the liberation of CX-3543 from lysosomes. This effect amplified both the inhibition of DNA-to-RNA transcription and cell death induced by CX-3543. Similar effects were observed when chloroquine derivatives were combined with CX-5461. Furthermore, combining CX-3543 with the chloroquine derivative DC661 reduced the growth of fibrosarcoma established in immunocompetent mice more efficiently than either agent alone. Altogether, our results uncover an unanticipated lysosome-related mechanism that contributes to the resistance of cancer cells to POL I transcription inhibitors, as well as a strategy to combat this resistance.

cancer biology↗

bioRxiv2024

G-quadruplexes in Haloferax volcanii

Archaea, a domain of microorganisms found in diverse environments including the human microbiome, represent the closest known prokaryotic relatives of eukaryotes. This phylogenetic proximity positions them as a relevant model for investigating the evolutionary origins of nucleic acid secondary structures such as G-quadruplexes (G4s), which play regulatory roles in transcription and replication. Although G4s have been extensively studied in eukaryotes, their presence and function in archaea remain poorly characterized. In this study, a genome-wide analysis of the halophilic archaeon Haloferax volcanii identified over 5, 800 potential G4-forming sequences. Biophysical validation confirmed that many of these sequences adopt stable G4 conformations in vitro. Using G4-specific detection tools and super-resolution microscopy, G4 structures were visualized in vivo in both DNA and RNA across multiple growth phases. Comparable findings were observed in the thermophilic archaeon Thermococcus barophilus. Functional analysis using helicase-deficient H. volcanii strains further identified candidate enzymes involved in G4 resolution. These results establish H. volcanii as a tractable archaeal model for G4 biology.

molecular biology↗