The PALB2 DNA-binding domain is an intrinsically disordered recombinase

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• The Partner and Localizer of BRCA2 (PALB2) protein is crucial for homologous recombination (HR) DNA repair by linking BRCA1 and BRCA2.
• PALB2's DNA-binding domain (PALB2-DBD) is known to support DNA strand exchange, a complex process vital for genomic stability.
• The precise mechanisms of PALB2-DBD's DNA interaction and its role in strand exchange remained largely uncharacterized.

Approach:

• Utilized biophysical techniques including circular dichroism, electron paramagnetic resonance, and small-angle X-ray scattering to investigate PALB2-DBD structure and dynamics.
• Performed bioinformatics analysis to further support the structural characterization of PALB2-DBD.
• Employed confocal single-molecule Förster Resonance Energy Transfer (smFRET) to observe DNA compaction upon PALB2-DBD binding.

Key Points:

• PALB2-DBD was determined to be intrinsically disordered, maintaining this state even when bound to DNA.
• Intrinsically disordered proteins (IDPs) are increasingly recognized for diverse biological roles, and PALB2-DBD's function in DNA strand exchange expands this repertoire.
• PALB2-DBD binding induces DNA compaction in an oligomerization-dependent manner.

Conclusions:

• Hypothesize that PALB2-DBD functions as a molecular chaperone, facilitating the formation and resolution of DNA/RNA intermediates during replication and repair.
• The predicted strong liquid-liquid phase separation (LLPS) potential of PALB2-DBD suggests a role for protein-nucleic acid condensates in its function.
• DNA-binding intrinsically disordered regions like PALB2-DBD may constitute a novel class of functional domains in eukaryotic nucleic acid metabolism.