Identification of Guanine-Quadruplex-Binding Peptides from the RGG3 Domain of TLS/FUS

Guanine quadruplexes (G4s) are non-canonical nucleic acid structures that have emerged as attractive therapeutic targets owing to their involvement in diverse biological processes. Additionally, peptides derived from G4-binding proteins provide promising platforms for selective G4 recognition. In this study, we explored the G4-binding capacity of arginine-glycine-glycine (RGG)-rich sequences derived from the RGG3 domain translocated in liposarcoma/fused in sarcoma (TLS/FUS), a known G4 RNA binding protein. In this study, we synthesized a library of overlapping 15-mer peptides and evaluated their G4-binding affinities. Among the 10 evaluated native sequences, several peptides demonstrated measurable affinities toward G4 RNA structures, with STK5-1 exhibiting the highest G4-binding affinity. Furthermore, to investigate the impact of conformational constraints on G4 recognition, we introduced (E)-methylalkene dipeptide isosteres (MADIs) into selected Gly-Gly motifs, generating a series of RGG peptidomimetics. Subsequent binding assays revealed that some of these MADI peptidomimetics exhibited enhanced affinity and selectivity compared with their unmodified counterparts. Our findings offer new insights into the sequence and structural features governing G4-binding, establishing a foundation for the further development of peptide-based G4 ligands.