Histones and Nucleosomes in Archaea

描述（由申请人提供）：古细菌组蛋白与真核小体核心组蛋白和许多大型真核转录因子亚基的组蛋白折叠具有共同的祖先。组蛋白折叠是指导二聚体形成的结构基序，古菌组蛋白形成同二聚体和异二聚体，但真核组蛋白折叠现在只形成异二聚体。古菌组蛋白也可以结合DNA，自发或单独地组装成复合物，并可以将DNA包裹在一个负的或正的超级线圈中。因此，它们提供了一个独特的机会和一个实用的实验系统来建立组蛋白：组蛋白和组蛋白：DNA相互作用的分子决定因素。提出的实验将产生对组蛋白折叠伴侣特异性，组蛋白-DNA亲和力，组蛋白组装定位以及DNA超卷曲方向决定因素的详细结构理解。这些都是理解基因组组织以及组蛋白和组蛋白折叠复合物在真核生物和古细菌中调节基因表达中的作用的核心和基础问题。获得的信息对于理解这些分子组装和相互作用中的缺陷如何对人类发育和健康产生负面影响也很重要。我们已经确定，不同的古菌组蛋白组装具有序列依赖性的DNA亲和差异，这提出了一个基于替代组蛋白二聚体组装的基因调控的全新概念。染色质免疫沉淀结合DNA微阵列杂交将用于研究这一新的想法，并验证该古菌组蛋白调控系统是真核生物基因组沉默和定位核小体组装基因调控的基础。

DESCRIPTION (provided by applicant): Archaeal histones share a common ancestry with the histone-folds of the eukaryotic nucleosome cores histones and subunits of many large eukaryotic transcription factors. The histone fold is a structural motif that directs dimer formation, and archaeal histones form homodimers and heterodimers but eukaryotic histone folds now form only heterodimers. Archaeal histones also bind DNA and assemble into complexes spontaneously and individually, and can wrap DNA in either a negative or positive supercoil. They therefore provide a unique opportunity, and a practical experimental system to establish the molecular determinants of histone:histone and histone:DNA interactions. The experiments proposed will generate a detailed structural understanding of histone fold partner specificity, histone-DNA affinity, the positioning of histone assembly, and the determinants of the direction of DNA supercoiling. These are all issues of central and fundamental importance to understanding genome organization and the roles of histones and histone foldcontaining complexes in regulating gene expression in Eukaryotes, and in Archaea. The information gained will also be of importance in understanding how defects in these molecular assemblies and interactions negatively impact human development and health. We have established that different archaeal histone assemblies have sequence-dependent differences in DNA affinity, and this suggests an entirely novel concept for gene regulation based on alternative histone dimer assembly. Chromatin immunoprecipitation coupled with DNA microarray hybridization will be used to investigate this new idea, and to test the hypothesis that this archaeal histone regulatory system was the foundation for eukaryotic genome silencing and gene regulation by positioned nucleosome assembly.