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Biopolym. Cell. 2026; 42(1):44-53.
http://dx.doi.org/10.7124/bc.000B34
Structure and Function of Biopolymers
Intrinsically Disordered Region 2 of G3BP1 is required for RNA recruitment by G3BP1-Caprin1 complex
1, 2Lavrynenko K. D., 1Hamon L., 2Kropyvko S. V.
  1. The laboratory «Structure and Activity of Normal and Pathological Biomolecules», Paris-Saclay University, Inserm, University of Évry
    Évry, France, 91025
  2. Institute of Molecular Biology and Genetics, NAS of Ukraine
    150, Akademika Zabolotnoho Str., Kyiv, Ukraine, 03143

Abstract

Aim. The stress granule assembly requires coordinated interactions between RNA-binding proteins and mRNA, yet how the intrinsically disordered regions (IDRs) of stress granule proteins regulate RNA recruitment remains incompletely understood. The aim of this study was to characterize a role of the Intrinsically Disordered Region 2 (IDR2) of Ras GTPase-activating protein-binding protein 1(G3BP1) in mRNA recruitment within the G3BP1-Caprin1 complex. Methods. Protein-protein and protein-RNA interactions in cells were analyzed as colocalization of their fluorescent signals on microtubules (microtubule bench recruitment and mixing assay). Nucleic acid-binding properties of G3BP1, G3BP1-ΔIDR2, a G3BP1 variant with deletion of IDR2, and G3BP1-Caprin1 complex were assessed in vitro by electrophoretic mobility shift assays. Results. Deletion of IDR2 strongly impaired mRNA recruitment by G3BP1 despite the presence of intact RNA-binding domains. G3BP1-ΔIDR2 retained the ability to interact with Caprin1 and exhibited robust heterotypic mixing in the cellular context. However, neither Caprin1 nor other G3BP1 partners were able to compensate for the loss of mRNA recruitment. In vitro assays confirmed reduced nucleic acid binding by G3BP1-ΔIDR2 and showed that Caprin1 did not compensate for the lossof G3BP1-ΔIDR2 nucleic acid binding. These findings indicate that impaired mRNA recruitment is not caused by the altered compartmentalization but reflects an intrinsic defect associated with IDR2 loss. Conclusions. Our results demonstrate that IDR2 plays a critical, indirect role in G3BP1-mediated mRNA recruitment by maintaining an RNA-binding-competent conformation of this protein. This study highlights the importance of intrinsically disordered regions in regulating mRNA engagement through conformational and structural effects rather than direct RNA binding and provides new insight into the molecular principles underlying stress granule assembly.
Keywords: messenger RNA-binding proteins, G3BP1, Caprin1, protein-protein interactions, protein-mRNA interactions
Full text: (PDF, in English)

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