Nanoscale Structure and Dynamics of Chromatin

本研究的目的是促进对着丝粒的结构和组装的基本理解，着丝粒是染色体的特殊片段，使它们能够在细胞分裂过程中准确分离。该项目将利用尖端的分子生物物理学方法来探测着丝粒组织相对于染色体其他部分的关键差异。科学技术进步将融入本科生和研究生的实践研究训练，并将纳入结构生物学和生物物理学的正式课程。将先进的技术应用于染色体生物学的核心问题，不仅可以激发学生对基础科学的兴趣，还可以为他们在生物学和物理学领域的职业生涯做好准备。在真核细胞中，细胞分裂过程中复制染色体的精确分离是由着丝粒介导的。如果着丝粒受损或被移除，染色体就会随机分离，从而扰乱细胞分裂过程。着丝粒与其他染色体的不同之处在于它含有核小体（高阶染色质的dna -蛋白质构建块），其中典型的蛋白质组蛋白H3被一种称为CENP-A的相关组蛋白所取代。这种替换被认为赋予着丝粒新的结构组织，从而使其能够被分离机制所识别。然而，关于高度特异性识别的结构和机制的细节仍然不确定。本项目的研究旨在提高对着丝粒各层次染色质结构的认识，特别是了解染色体的着丝粒与非着丝粒区域的结构特征。高分辨率原子力显微镜（AFM）研究将用于评估着丝粒染色质在不同组织水平上的结构。单核小体和核小体阵列将使用尖端的高速原子力显微镜直接可视化，实现纳米级水溶液的动态成像，具有视频速率的时间分辨率。实验数据将辅以大功率的计算分析。这种结合的方法将揭示着丝粒核小体和核小体阵列的结构和动力学，并将有助于理解在染色体分离过程中着丝粒结构与其功能之间的关系。该项目由分子和细胞生物科学部的遗传机制项目、生物科学理事会的新兴前沿部门以及数学和物理科学理事会物理部的生命系统物理学项目共同资助。

The goal of this research is to advance fundamental understanding of the structure and assembly of centromeres, the specialized segments of chromosomes that allow them to separate accurately during cell division. The project will take advantage of cutting-edge molecular biophysics approaches to probe key differences in the organization of centromeres, relative to other parts of chromosomes. Scientific and technological advances will be integrated into hands-on research training for undergraduate and graduate students and will be incorporated into a formal course of study in structural biology and biophysics. Application of state-of-the art technology to central questions in chromosome biology is expected not only to inspire student interest in basic science, but also to prepare them for careers at the interface of biology and physics. In eukaryotic cells, accurate segregation of replicated chromosomes during cell division is mediated by centromeres. If centromeres become damaged or removed, chromosomes segregate randomly, thus disrupting the cell division process. Centromeres differ from the rest of the chromosomes by containing nucleosomes (DNA-protein building blocks of higher-order chromatin) in which the typical protein histone H3 has been replaced by a related histone known as CENP-A. This replacement is presumed to confer new structural organization to the centromere, thereby enabling it to be recognized by the segregation machinery. However, details about the structure and the mechanism underlying the highly specific recognition remain uncertain. The studies in this project are designed to advance knowledge of centromere chromatin structure at all levels of its organization and especially to understand what structural features distinguish centromeres from non-centromeric regions of chromosomes. High-resolution atomic force microscopy (AFM) studies will be used to assess the structure of centromere chromatin at different levels of organization. Single nucleosomes and nucleosome arrays will be visualized directly with the use of cutting-edge high-speed AFM, enabling dynamic imaging in aqueous solution at nanoscale with video-rate temporal resolution. The experimental data will be supplemented by high-power computational analysis. This combined approach will shed new light on the structure and dynamics of centromere nucleosomes and nucleosome arrays and will lead to understanding the relationship between centromere structure and its function during the chromosomal segregation process. This project is co-funded by the Genetic Mechanisms Program in the Division of Molecular and Cellular Biosciences and by the Emerging Frontiers Division, both in the Biological Sciences Directorate, and by the Physics of Living Systems Program in the Physics Division in the Mathematical and Physical Sciences Directorate.