SUBUNIT STRUCTURE OF CHROMATIN

这项研究的总体目标是有助于理解 染色质的结构和动力学--尤其是，如何 结构可以根据工艺中所涉及的应力而改变 比如转录和复制。一套基本的知识体系 这样的理解是关于分子的热力学稳定性的数据 核小体，染色质结构的单一成分。这样的信息 将通过对重组系统的物理研究来寻求，使用 携带定位序列的DNA分子的克隆和纯化 组蛋白低聚物。DNA与DNA的缔合-解离平衡 将首先研究(H3-H4)2四聚体，然后分析 这样形成的络合物与(H_2A-H_2B)二聚体反应。比较 稳定性研究将考察不同地区对 DNA序列稳定。最后，进行了一系列的实验，利用 一个非常小的“微染色体”的不同拓扑形式 三个核小体位置)将被用于分析 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.