Zhang Meng, Celis César-Díaz, Liu Jianfang, Bustamante Carlos, Ren Gang
The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA.
Applied Science and Technology Graduate Group, University of California, Berkeley, USA.
Res Sq. 2023 Jan 19:rs.3.rs-2460504. doi: 10.21203/rs.3.rs-2460504/v1.
Chromatin phase transition serves as a regulatory mechanism for eukaryotic transcription. Understanding this process requires the characterization of the nucleosome array structure in response to external stimuli prior to phase separation. However, the intrinsic flexibility and heterogeneity hinders the arrays' structure determination. Here we exploit advances in cryogenic electron tomography (cryo-ET) to determine the three-dimensional (3D) structure of each individual particle of mono-, di-, tri-, and tetranucleosome arrays. Statistical analysis reveals the ionic strength changes the angle between the DNA linker and nucleosome core particle (NCP), which regulate the overall morphology of nucleosome arrays. The finding that one-third of the arrays in the presence of H1 contain an NCP invaded by foreign DNA suggests an alternative function of H1 in constructing nucleosomal networks. The new insights into the nucleosome conformational changes prior to the intermolecular interaction stage extends our understanding of chromatin phase separation regulation.
染色质相变作为真核生物转录的一种调控机制。要理解这一过程，需要在相分离之前表征核小体阵列结构对外部刺激的响应。然而，其固有的灵活性和异质性阻碍了阵列结构的确定。在这里，我们利用低温电子断层扫描（cryo-ET）技术的进展来确定单核小体、双核小体、三核小体和四核小体阵列中每个单独颗粒的三维（3D）结构。统计分析表明，离子强度会改变DNA连接体与核小体核心颗粒（NCP）之间的角度，从而调节核小体阵列的整体形态。在存在H1的情况下，三分之一的阵列含有被外源DNA侵入的NCP，这一发现表明H1在构建核小体网络中具有另一种功能。对分子间相互作用阶段之前核小体构象变化的新见解扩展了我们对染色质相分离调控的理解。
