Intrinsically disordered SERBP1 regulates translation through topology-driven G-quadruplex recognition

Area of Science:

• Molecular Biology
• Structural Biology
• Cancer Research

Background:

• Serpine mRNA-binding protein 1 (SERBP1) is an intrinsically disordered protein implicated in cancer, but its RNA recognition mechanism is unclear.
• Understanding SERBP1's interaction with RNA targets is crucial for elucidating its role in translation regulation and disease.

Purpose of the Study:

• To characterize the G-quadruplex (G4)-binding properties of SERBP1.
• To elucidate the molecular mechanism of SERBP1-G4 recognition.
• To investigate the role of SERBP1-G4 interactions in glioblastoma and mTOR regulation.

Main Methods:

• NMR spectroscopy and biophysical assays to determine SERBP1-G4 binding affinity and mechanism.
• Molecular dynamics and docking simulations to visualize the interaction.
• Phosphomimetic mutations to assess the role of serine phosphorylation.
• Cell-based assays in glioblastoma to study SERBP1's role in mTOR expression.

Main Results:

• SERBP1 binds parallel RNA and DNA G4s with low micromolar affinity via an encircling mechanism involving its RGG box and C-terminal serines.
• Phosphorylation of key serines acts as a regulatory switch, modulating SERBP1 binding affinity.
• G4 topology, not sequence, drives SERBP1 recognition, positioning it as a broad-specificity G4 adaptor.
• SERBP1 regulates mTOR expression in glioblastoma through G4 elements in the mTOR 5' UTR, and its depletion synergizes with mTOR inhibition.

Conclusions:

• SERBP1 is a G4 adaptor protein that recognizes G4 structures through a unique encircling mechanism.
• Phosphorylation serves as a regulatory switch for SERBP1 activity.
• SERBP1-G4 interactions are critical for mTOR regulation in glioblastoma, presenting a potential therapeutic target.