Human BRCA1-BARD1 ubiquitin ligase activity counteracts chromatin barriers to DNA resection

Ruth M Densham, Alexander J Garvin, Helen R Stone, Joanna Strachan, Robert A Baldock, Manuel Daza-Martin, Alice Fletcher, Sarah Blair-Reid, James Beesley, Balraj Johal, Laurence H Pearl, Robert Neely, Nicholas H Keep, Felicity Z Watts, Joanna R Morris

Research output: Contribution to journalArticlepeer-review

Abstract

The opposing activities of 53BP1 and BRCA1 influence pathway choice in DNA double-strand-break repair. How BRCA1 counteracts the inhibitory effect of 53BP1 on DNA resection and homologous recombination is unknown. Here we identify the site of BRCA1-BARD1 required for priming ubiquitin transfer from E2∼ubiquitin and demonstrate that BRCA1-BARD1's ubiquitin ligase activity is required for repositioning 53BP1 on damaged chromatin. We confirm H2A ubiquitination by BRCA1-BARD1 and show that an H2A-ubiquitin fusion protein promotes DNA resection and repair in BARD1-deficient cells. BRCA1-BARD1's function in homologous recombination requires the chromatin remodeler SMARCAD1. SMARCAD1 binding to H2A-ubiquitin and optimal localization to sites of damage and activity in DNA repair requires its ubiquitin-binding CUE domains. SMARCAD1 is required for 53BP1 repositioning, and the need for SMARCAD1 in olaparib or camptothecin resistance is alleviated by 53BP1 loss. Thus, BRCA1-BARD1 ligase activity and subsequent SMARCAD1-dependent chromatin remodeling are critical regulators of DNA repair.

Original languageEnglish
Pages (from-to)647-55
Number of pages9
JournalNature Structural and Molecular Biology
Volume23
Issue number7
DOIs
Publication statusPublished - 30 May 2016
Externally publishedYes

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