Cell-Active Peptide Inhibitors of the FANCM-RMI Interaction.

Area of Science:

• Biochemistry
• Molecular Biology
• Cancer Research

Background:

• The FANCM-RMI protein interaction is vital for the Alternative Lengthening of Telomeres (ALT) pathway, a mechanism used by cancers to achieve replicative immortality.
• Targeting this interaction offers a potential therapeutic strategy for ALT-driven cancers.

Purpose of the Study:

• To discover and characterize the first cell-active peptide inhibitors of the FANCM-RMI protein-protein interaction.
• To develop chemical tools for investigating the role of FANCM-RMI in ALT-positive cancers.

Main Methods:

• Screening of mRNA-displayed peptide libraries using trans-1,4-dibromo-2-butene.
• Characterization of peptide binding affinity to RMI using nanomolar affinity measurements (K_D).
• X-ray crystallography to determine the binding mode of the top peptide inhibitor.
• Assessment of antiproliferative effects in ALT-positive osteosarcoma cell lines after conjugation to cell-penetrating peptides.

Main Results:

• Discovery of potent linear and cyclic peptide inhibitors that bind RMI at the FANCM interaction site with nanomolar affinity (K_D = 4-31 nM).
• Peptide inhibitors outcompeted the native FANCM peptide mimic (IC₅₀ = 24-155 nM).
• X-ray crystal structure revealed novel interactions between the top peptide hit and RMI.
• Cell-penetrating peptide conjugates demonstrated antiproliferative effects in ALT-positive osteosarcoma cells.

Conclusions:

• The study reports the first cell-active peptide inhibitors of the FANCM-RMI interaction.
• These inhibitors are valuable chemical tools for studying the FANCM-RMI complex in ALT-driven cancers.
• The findings open new avenues for therapeutic strategies targeting cancers utilizing the ALT pathway.