Targeting nucleolin by RNA G-quadruplex-forming motif

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• High nucleolin (NCL) expression correlates with poor lung cancer (LC) prognosis, indicating its potential as a biomarker.
• Nucleolin exhibits a strong affinity for binding G-quadruplexes (G4).

Purpose of the Study:

• Investigate the formation of an RNA quadruplex structure in the human precursor pre-MIR150 sequence (rG4) capable of NCL recognition.
• Evaluate rG4 as a potential diagnostic and prognostic tool for lung cancer.

Main Methods:

• Circular dichroism (CD) spectroscopy to analyze rG4 structure and stability.
• Thermal stability assays in the presence and absence of PhenDC3.
• Polyacrylamide gel electrophoresis (PAGE) to study complex formation.
• Enzyme-linked immunosorbent assay (ELISA) for NCL expression analysis in liquid biopsies.

Main Results:

• The pre-MIR150 G4-forming sequence (rG4) forms a parallel quadruplex structure, exhibiting high thermal stability.
• rG4 demonstrates nanomolar binding affinity to both PhenDC3 and NCL RBD1,2, forming a ternary complex.
• Fluorescently labeled rG4 successfully recognizes NCL-positive cells.
• ELISA revealed altered NCL expression in LC patient liquid biopsies.

Conclusions:

• The rG4 structure is stable and binds NCL with high affinity, suggesting its potential as a molecular probe.
• Labeled rG4 can serve as a detection probe for NCL-positive cells and lung cancer in liquid biopsies.
• NCL expression patterns in liquid biopsies may aid in LC diagnosis, prognosis, and treatment monitoring.