ジャーナル: Nucleic Acids Res / 年: 2023 タイトル: BRCA1-BARD1 combines multiple chromatin recognition modules to bridge nascent nucleosomes. 著者: Hayden Burdett / Martina Foglizzo / Laura J Musgrove / Dhananjay Kumar / Gillian Clifford / Lisa J Campbell / George R Heath / Elton Zeqiraj / Marcus D Wilson / 要旨: Chromatin association of the BRCA1-BARD1 heterodimer is critical to promote homologous recombination repair of DNA double-strand breaks (DSBs) in S/G2. How the BRCA1-BARD1 complex interacts with ...Chromatin association of the BRCA1-BARD1 heterodimer is critical to promote homologous recombination repair of DNA double-strand breaks (DSBs) in S/G2. How the BRCA1-BARD1 complex interacts with chromatin that contains both damage induced histone H2A ubiquitin and inhibitory H4K20 methylation is not fully understood. We characterised BRCA1-BARD1 binding and enzymatic activity to an array of mono- and di-nucleosome substrates using biochemical, structural and single molecule imaging approaches. We found that the BRCA1-BARD1 complex preferentially interacts and modifies di-nucleosomes over mono-nucleosomes, allowing integration of H2A Lys-15 ubiquitylation signals with other chromatin modifications and features. Using high speed- atomic force microscopy (HS-AFM) to monitor how the BRCA1-BARD1 complex recognises chromatin in real time, we saw a highly dynamic complex that bridges two nucleosomes and associates with the DNA linker region. Bridging is aided by multivalent cross-nucleosome interactions that enhance BRCA1-BARD1 E3 ubiquitin ligase catalytic activity. Multivalent interactions across nucleosomes explain how BRCA1-BARD1 can recognise chromatin that retains partial di-methylation at H4 Lys-20 (H4K20me2), a parental histone mark that blocks BRCA1-BARD1 interaction with nucleosomes, to promote its enzymatic and DNA repair activities.
モデル: Quantifoil R3.5/1 / 材質: COPPER / メッシュ: 200 / 前処理 - タイプ: GLOW DISCHARGE / 前処理 - 時間: 30 sec. / 前処理 - 雰囲気: AIR 詳細: Quantifoil R3.5/1 200-mesh grids (Quantifoil Micro Tools GmbH) were glow-discharged for 30 s at 40 mA using a GloQube (Quorum) glow discharge unit
凍結
凍結剤: ETHANE / チャンバー内湿度: 100 % / チャンバー内温度: 277 K / 装置: FEI VITROBOT MARK IV / 詳細: blot force = 0 N blot time = 8 s.
詳細
Purified cat BRCA1dExon11-FL BARD1 (at 3 uM) was incubated with H2AKc15ub mono-nucleosomes (at 1.5 uM) for 1 h on ice before cryo-EM grids preparation
-
電子顕微鏡法
顕微鏡
FEI TITAN KRIOS
撮影
フィルム・検出器のモデル: FEI FALCON IV (4k x 4k) 撮影したグリッド数: 1 / 実像数: 16015 / 平均露光時間: 5.0 sec. / 平均電子線量: 36.37 e/Å2
モデルのタイプ: OTHER 詳細: The start up model was generated directly from this dataset, following 2D Classification and Ab Initio Reconstruction in cryoSPARC 3.2.0