Antiparallel Coiled-Coil Interactions Mediate the Homodimerization of the DNA Damage-Repair Protein PALB2

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Deficits in DNA damage repair pathways are linked to cancer.
• Homologous recombination (HR) is a key mechanism for repairing DNA double-strand breaks in mammalian cells.
• Partner and localizer of BRCA2 (PALB2) is essential for HR, interacting with BRCA1 and BRCA2 at break sites.

Purpose of the Study:

• To investigate the role of PALB2 homodimerization in HR.
• To characterize the structural and functional properties of the PALB2 coiled-coil (PALB2cc) domain.
• To determine how PALB2cc homodimerization affects interactions with BRCA1cc and its impact on genomic stability.

Main Methods:

• Production and structural determination of PALB2cc homodimers using solution NMR spectroscopy.
• NMR chemical-shift perturbation studies to analyze PALB2cc homodimer and PALB2cc/BRCA1cc heterodimer formation.
• Site-directed mutagenesis (Leu24) to assess the impact on dimer stability and cellular function.

Main Results:

• PALB2cc forms stable antiparallel coiled-coil homodimers, confirmed by NMR.
• PALB2cc also forms heterodimers with BRCA1cc.
• Mutation of Leu24 in PALB2cc significantly destabilizes homodimers but has a milder effect on heterodimers.
• The Leu24 mutation causes genomic instability and reduced cell viability following DNA double-strand break induction.

Conclusions:

• PALB2cc homodimerization is structurally distinct from its heterodimerization with BRCA1cc.
• PALB2 homodimerization plays a significant role in maintaining genomic stability and cell viability.
• These findings provide insights into specific mutations affecting PALB2 function in HR and cancer.