Histones and Nucleosomes in Archaea

描述（由申请人提供）：真核细胞组蛋白与真核细胞核小体核心组蛋白和许多大的真核细胞转录因子的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，古细菌组蛋白形成同源二聚体和异源二聚体，但真核生物组蛋白折叠现在只形成异源二聚体。微囊膜组蛋白也能结合DNA并自发地和单独地组装成复合物，并且可以将DNA包裹在负超螺旋或正超螺旋中。因此，他们提供了一个独特的机会，和一个实用的实验系统，以建立组蛋白：组蛋白和组蛋白：DNA相互作用的分子决定簇。提出的实验将产生一个详细的结构理解组蛋白折叠伴侣特异性，组蛋白-DNA亲和力，组蛋白组装的定位，和DNA超螺旋方向的决定因素。这些都是理解基因组组织和组蛋白和组蛋白foldcontaining复合物在调节真核生物基因表达中的作用的核心和根本重要性的问题，在Eukaryotes，并在Escherea。获得的信息也将是重要的，在了解这些分子组装和相互作用的缺陷如何负面影响人类的发展和健康。我们已经确定，不同的古细菌组蛋白组件有序列依赖性的DNA亲和力的差异，这表明了一个全新的概念，基因调控的基础上替代组蛋白二聚体组装。染色质免疫沉淀结合DNA微阵列杂交将被用来调查这一新的想法，并测试假设，这古组蛋白调控系统是真核基因组沉默和基因调控的基础定位核小体组装。

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.