G-quadruplex ligands exclude RNA-binding RGG peptides from G-quadruplex condensates, modulating liquid-liquid phase separation
Background
Biomolecular liquid-liquid phase separation (LLPS), forming cellular droplets, is crucial for gene expression regulation. Dysfunction in LLPS can lead to aberrant aggregates that sequester RNA-binding proteins, impairing their function and potentially contributing to neurodegenerative diseases. Preventing or reversing this sequestration is a promising therapeutic strategy. The G-quadruplex, a non-canonical nucleic acid structure, is a key motif that triggers LLPS with partner proteins. Thus, G-quadruplex ligands, which selectively bind and stabilize these structures, offer a novel approach to control G-quadruplex-mediated LLPS.
Study Design
Researchers investigated the effects of G-quadruplex ligands on the liquid-liquid phase separation of RNA G-quadruplexes and RGG domain-derived cationic peptides in an in vitro setting. The study focused on observing the formation of aggregates and the subsequent exclusion of the G-quadruplex-binding peptides. They also assessed the structure-selectivity of these ligands, testing their ability to induce aggregates specifically with G-quadruplexes versus other secondary nucleic acid structures. The primary endpoint was the modulation of condensate formation and composition.
Results
G-quadruplex ligands were found to form aggregates with their target RNA G-quadruplexes. Crucially, these aggregates effectively excluded the RGG domain-derived cationic peptides that typically bind to G-quadruplexes. This exclusion demonstrates a novel mechanism by which ligands can modulate the composition of biomolecular condensates. The study further revealed that structure-selective G-quadruplex ligands induced aggregates exclusively with the G-quadruplex structure, showing no such interaction with other nucleic acid secondary structures. This selectivity highlights the precision of these ligands in targeting specific biomolecular assemblies.
This is the first demonstration that the structure-selectivity of G-quadruplex ligands is a key factor in modulating biomolecular condensates.
Key Findings
- G-quadruplex ligands formed aggregates with RNA G-quadruplexes.
- These ligand-G-quadruplex aggregates effectively excluded RGG domain-derived cationic peptides.
- Structure-selective G-quadruplex ligands induced aggregates only with G-quadruplexes, not other structures.
- Structure-selectivity of G-quadruplex ligands is key to modulating biomolecular condensates.
Why It Matters
This research provides a foundational understanding of how G-quadruplex ligands can precisely modulate liquid-liquid phase separation (LLPS) by controlling the inclusion or exclusion of RNA-binding proteins. For those interested in neurodegenerative diseases, this opens a new avenue for therapeutic intervention by targeting aberrant protein sequestration. The practical takeaway is that structure-selective G-quadruplex ligands could be designed to rescue RNA-binding protein function by preventing their pathological aggregation. While currently an in-vitro finding, it lays the groundwork for developing novel compounds that could restore cellular homeostasis in conditions linked to LLPS dysfunction, potentially leading to future drug development for complex neurological disorders.
g-quadruplex
rna-binding-proteins
liquid-liquid-phase-separation
neurodegenerative-diseases
in-vitro
rgg-peptide