EMD-23592

Single-particle
2.94 Å
EMD-23592 Deposition: 06/03/2021
Map released: 16/06/2021
Last modified: 09/10/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links

EMD-23592

Cryo-EM structure of the human nucleosome core particle ubiquitylated at histone H2A Lys13 and Lys15 in complex with BARD1 (residues 415-777)

EMD-23592

Single-particle
2.94 Å
EMD-23592 Deposition: 06/03/2021
Map released: 16/06/2021
Last modified: 09/10/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Homo sapiens
Sample: Human nucleosome core particle ubiquitylated at histone H2A Lys13 and Lys15 in complex with BARD1 (residues 415-777)
Fitted models: 7lyc (Avg. Q-score: 0.566)

Deposition Authors: Hu Q , Botuyan MV
Mechanisms of BRCA1-BARD1 nucleosome recognition and ubiquitylation.
Hu Q , Botuyan MV , Zhao D, Cui G, Mer E , Mer G
(2021) Nature , 596 , 438 - 443
PUBMED: 34321665
DOI: doi:10.1038/s41586-021-03716-8
ISSN: 1476-4687
ASTM: NATUAS
Abstract:
The BRCA1-BARD1 tumour suppressor is an E3 ubiquitin ligase necessary for the repair of DNA double-strand breaks by homologous recombination1-10. The BRCA1-BARD1 complex localizes to damaged chromatin after DNA replication and catalyses the ubiquitylation of histone H2A and other cellular targets11-14. The molecular bases for the recruitment to double-strand breaks and target recognition of BRCA1-BARD1 remain unknown. Here we use cryo-electron microscopy to show that the ankyrin repeat and tandem BRCT domains in BARD1 adopt a compact fold and bind to nucleosomal histones, DNA and monoubiquitin attached to H2A amino-terminal K13 or K15, two signals known to be specific for double-strand breaks15,16. We further show that RING domains17 in BRCA1-BARD1 orient an E2 ubiquitin-conjugating enzyme atop the nucleosome in a dynamic conformation, primed for ubiquitin transfer to the flexible carboxy-terminal tails of H2A and variant H2AX. Our work reveals a regulatory crosstalk in which recognition of monoubiquitin by BRCA1-BARD1 at the N terminus of H2A blocks the formation of polyubiquitin chains and cooperatively promotes ubiquitylation at the C terminus of H2A. These findings elucidate the mechanisms of BRCA1-BARD1 chromatin recruitment and ubiquitylation specificity, highlight key functions of BARD1 in both processes and explain how BRCA1-BARD1 promotes homologous recombination by opposing the DNA repair protein 53BP1 in post-replicative chromatin18-22. These data provide a structural framework to evaluate BARD1 variants and help to identify mutations that drive the development of cancer.