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.
詳細: 25 mM HEPES pH 7.5, 300 mM NaCl, 5% (v/v) glycerol and 1 mM TCEP
グリッド
モデル: UltrAuFoil R1.2/1.3 / 材質: GOLD / メッシュ: 300 / 支持フィルム - 材質: GOLD / 支持フィルム - トポロジー: HOLEY / 前処理 - タイプ: PLASMA CLEANING / 前処理 - 時間: 60 sec. / 前処理 - 雰囲気: AIR 詳細: UltrAuFoil R1.2/1.3 300-mesh gold grids (Quantifoil Micro Tools GmbH) were cleaned via indirect plasma using a Tergeo EM plasma cleaner (Pie Scientific) at 15 W for 1 min, and with flow rates ...詳細: UltrAuFoil R1.2/1.3 300-mesh gold grids (Quantifoil Micro Tools GmbH) were cleaned via indirect plasma using a Tergeo EM plasma cleaner (Pie Scientific) at 15 W for 1 min, and with flow rates for nitrogen, oxygen and argon gasses of 20.0, 19.8 and 29.0 sscm respectively
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: Vitrification was carried out by using a blot force of 6 N and a blot time of 6 s.
-
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 III (4k x 4k) 検出モード: INTEGRATING / 撮影したグリッド数: 1 / 実像数: 227 / 平均露光時間: 1.7 sec. / 平均電子線量: 73.0 e/Å2
選択した数: 117630 詳細: Initially, 1,368 particles were manually picked and used to train crYOLO v1.6.1. This trained model was used for picking on all 227 movies, resulting in 117,630 particles
初期モデル
モデルのタイプ: OTHER 詳細: The startup model was derived from this same data following 2D Classification and Ab Initio Reconstruction in cryoSPARC