Protein Condensates Unfold G-Quadruplex Resembling a Helicase Activity

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Membrane-less organelles form via liquid-liquid phase separation, playing key roles in cellular functions.
• G-quadruplex (G4) structures, a noncanonical nucleic acid formation, interact with scaffolding proteins within these organelles.
• The structural and stability characteristics of G4s integrated into phase-separated condensates are not well understood.

Purpose of the Study:

• To investigate the conformational changes and stability of a G-quadruplex (G4) structure within phase-separated condensates.
• To elucidate the role of the disordered protein DDX4N1 in modulating G4 structure during phase separation.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study G4 conformation.
• Other biophysical techniques were utilized to assess structural and stability features.
• The study focused on the human telomeric sequence MHT24 within DDX4N1 condensates.

Main Results:

• The MHT24 sequence, known to form a G4 structure, was observed to unfold within DDX4N1 condensates.
• This unfolding occurred specifically due to the liquid-liquid phase separation process.
• The protein DDX4N1 influenced the G4 structure stability within the condensed phase.

Conclusions:

• Protein condensates can induce structural changes, such as unfolding, in integrated G-quadruplex structures.
• This finding demonstrates a novel mechanism by which proteins gain functionality through phase separation.
• The study enhances understanding of how protein condensates regulate G4 structure and cellular functions.