Two Missense Variants Detected in Breast Cancer Probands Preventing BRCA2-PALB2 Protein Interaction

Area of Science:

• Genetics and Molecular Biology
• Cancer Research
• Biochemistry

Background:

• Germline pathogenic variants in DNA repair genes BRCA1, BRCA2, and PALB2 are linked to increased breast cancer risk.
• Variants of Uncertain Significance (VUSs), particularly missense variants, pose challenges in clinical risk assessment due to limited data.
• Functional analyses are crucial for classifying VUSs and understanding their impact on protein function.

Purpose of the Study:

• To functionally characterize two unclassified missense variants, BRCA2:c.91T >G (p.Trp31Gly) and PALB2:c.3262C >T (p.Pro1088Ser), detected in breast cancer patients.
• To assess the impact of these variants on the interaction between BRCA2 and PALB2 proteins.
• To provide evidence for the potential pathogenicity of these variants.

Main Methods:

• Utilized a green fluorescent protein (GFP)-reassembly in vitro assay to evaluate the BRCA2-PALB2 interaction.
• Tested the functional effect of BRCA2:p.Trp31Gly and PALB2:p.Pro1088Ser variants on protein binding.
• Compared variant effects to normal and mutant controls.

Main Results:

• The functional assay demonstrated that both BRCA2:p.Trp31Gly and PALB2:p.Pro1088Ser variants disrupt the binding between BRCA2 and PALB2 proteins.
• These variants were located in critical protein-interaction domains and predicted as deleterious by in silico analyses.
• The assay proved to be a robust and reliable method for testing variants affecting protein interactions.

Conclusions:

• The functional data suggest that BRCA2:p.Trp31Gly and PALB2:p.Pro1088Ser variants may be pathogenic by impairing the BRCA2-PALB2 interaction.
• Functional studies provide valuable evidence for classifying rare VUSs, aiding in breast cancer risk assessment.
• Further clinical correlation is warranted, but these findings contribute to understanding the role of these variants in DNA repair and cancer predisposition.