DNA length tunes the fluidity of DNA-based condensates

Area of Science:

• Biophysics
• Molecular Biology
• Genomics

Background:

• Genomic DNA is stored in condensed forms within living organisms.
• DNA condensation mechanisms include macromolecular crowding, multivalent cations, and proteins.
• DNA condensates can exhibit liquid-like or solid-like properties depending on DNA characteristics and solvent composition.

Purpose of the Study:

• To systematically investigate the impact of DNA length on the properties of DNA condensates.
• To understand how DNA length influences the transition from liquid-like to solid-like condensate behavior.

Main Methods:

• Systematic assessment of DNA length influence on condensate properties.
• Condensation triggered by polyethylene glycol and magnesium ions, linker histone H1, or nucleosome reconstitution.
• Titration experiments with linker histone H1 to assess fluidity dependence.

Main Results:

• Short DNA molecules (<1 kb) form dynamic, liquid-like assemblies.
• Increasing DNA length leads to less dynamic, more solid-like assemblies (e.g., phage λ-DNA, 48.5 kb).
• A gradual transition from liquid-like to solid-like properties occurs with DNA lengths between 1-10 kb.

Conclusions:

• DNA length is a key determinant of condensate fluidity, with shorter DNA favoring liquid-liquid phase separation and longer DNA favoring solid-like condensates.
• The number of attractive interactions per DNA molecule influences condensate fluidity.
• Findings enhance understanding of DNA-involved biomolecular condensates and potential modulation of chromosomal domains.