SUBUNIT STRUCTURE OF CHROMATIN

本研究的总体目标是帮助了解 染色质的结构和动力学--特别是， 结构会随着过程中的应力而改变 比如转录和复制。一个知识体系， 这种理解是关于热力学稳定性的数据， 核小体，染色质结构的单一元件。此类信息 将通过对重组系统的物理研究， 克隆携带“定位”序列的DNA分子并纯化 组蛋白寡聚体。DNA与DNA的结合-解离平衡 首先研究（H3-H4）2四聚体，然后分析 如此形成的络合物与（H2 A-H2 B）二聚体的反应。比较 稳定性研究将检查不同地区的影响， DNA序列稳定性。最后，一系列实验利用 一个非常小的“微型染色体”的不同拓扑形式（包含 三个核小体位点）将被引导到分析 超螺旋张力对核小体稳定性的定量影响。

The overall objective of this research is to contribute to understanding of the structure and dynamics of chromatin--in particular, how that structure can change in response to the stresses involved in processes like transcription and replication. A body of knowledge fundamental to such understanding is data on the thermodynamic stability of the nucleosome, the unitary element of chromatin structure. Such information will be sought through physical studies of reconstituted systems, using cloned DNA molecules carrying "positioning" sequences and purified histone oligomers. The association-dissociation equilibria of DNA with the (H3-H4)2 tetramer will be first studied, followed by analysis of the reaction of the complex so formed with (H2A-H2B) dimers. Comparative stability studies will examine the effects of different regions in the DNA sequence on stability. Finally, a series of experiments utilizing different topological forms of a very small "minichromosome" (containing three nucleosome sites) will be directed toward an analysis of the quantitative effects of superhelical tension on nucleosome stability.