Decoding the BRCA2 reversion principles underlying PARP inhibitor resistance

BRCA2 reversion mutations that restore function are shaped by local sequence context and BRCA2 domain architecture, determining which reading-frame or splicing events become PARPi-resistant in BRCA2-mutant isogenic cells.

• Why it matters: PARPi resistance via BRCA2 reversion limits durable responses in BRCA2-mutant cancers, and predicting these events could guide treatment and improve interpretation of secondary variants.
• What they did: Using an isogenic cell system with CRISPR editing, the study maps how sequence context influences reading-frame restoration and how domain architecture selects resistant reversions, including DNA-level frame restoration and transcript-level rescue by alternative splicing.
• The result: Two restoration routes operate within and across exons, and exon 11 shows distinct mechanisms—large genomic deletions and recurrent splice isoforms that bypass the canonical splice donor—enabling a basis for a predictive code for PARPi resistance.

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