Histone Nuclear Import and Chromatin Assembly

描述(由申请人提供)：该项目的长期目标是了解核运输因子和组蛋白伴侣蛋白的功能是如何协调的，并调节组蛋白组装到特定的染色质区域。我们将确定组蛋白伴侣蛋白如何决定组蛋白在细胞中的运动，从而作为组蛋白功能的一般调节器。在每个细胞周期中，细胞的全部DNA内容都会被快速复制，并与新合成的组蛋白重新包装，形成核小体。此外，组蛋白与染色质中已有的组蛋白交换，以允许添加变异组蛋白，并允许聚合酶和DNA修复机制通过。组蛋白由核粘附素家族的特定成员输入到细胞核中。组蛋白伴侣蛋白也是组蛋白代谢中的关键角色，它在合成后不久就与组蛋白结合，并将它们护送到核小体。本项目的重点是组蛋白伴侣蛋白在组蛋白进出口中的作用，以及组蛋白伴侣蛋白是否调节组蛋白在细胞中的运动这一重要问题。这个项目建立在之前的观察基础上，即酵母组蛋白伴侣NAP1p是一个组蛋白核输入因子。具体地说，我们将检验这一假设，即特定的H3和H4组蛋白伴侣蛋白，如Asflp，调节组蛋白核的进出口。组蛋白伴侣Naplp作为H_2A.Z供体和受体，并调节H_2A.Z的细胞定位的假设将得到验证。最后将检验这一假设，即不同的可逆磷酸化事件调节NaPLP功能的周期，使其在细胞核和细胞质中发挥不同的作用。在最近的晶体结构背景下分析磷酸化位点将有助于理解NaPLP的调节机制。核小体的正确组装是维持所有细胞基因组稳定性的关键。参与核小体组装和重塑途径的蛋白质功能障碍也与人类疾病和癌症有关。这突出了在酵母组蛋白伴侣蛋白作为模式生物的功能解剖的重要性，并将为我们提供有关组蛋白伴侣蛋白在人类生理学和人类疾病中的作用的有用信息。

DESCRIPTION (provided by applicant): The long term goal of this project is to understand how the functions of nuclear transport factors and histone chaperones are coordinated, and regulate the assembly of histones into specific chromatin domains. We will determine how histone chaperones dictate the movement of histones in the cell and thereby serve as general regulators of histone function. Every cell cycle the entire DNA content of a cell is rapidly replicated and repackaged with newly synthesized histones to form nucleosomes. In addition histones are exchanged with those already in chromatin, to allow the addition of variant histones, and to allow passage of polymerases and DNA repair machineries. Histones are imported into the nucleus by specific members of the karyopherin family. Histone chaperones are also key players in histone metabolism that bind histones shortly after synthesis and escort them to the nucleosome. This project focuses on the role of histone chaperones in histone import and export, and the significant question of whether histone chaperones regulate the movement of histones in the cell. This project builds from previous observations that the yeast histone chaperone Nap1 p is a histone nuclear import factor. Specifically, we will test the hypothesis that specific histone chaperones for H3 and H4, such as Asflp, regulate histone nuclear import and export. The hypothesis that the histone chaperone Naplp acts as an H2A.Z donor and acceptor, and regulates the cellular localization of H2A.Z will be tested. Lastly the hypothesis will be tested that distinct reversible phosphorylation events regulate cycles of Naplp function, allowing it to perform distinct role in the nucleus and cytoplasm. Analysis of phosphorylation sites in the context of the recent crystal structure will allow an understanding of the mechanism of Naplp regulation. The correct assembly of nucleosomes is critical for maintaining genomic stability in all cells. The dysfunction of proteins involved in nucleosome assembly and remodeling pathways is also coincident with human disease and cancer. This highlights the importance of dissecting the function of histone chaperones in yeast as a model organism, and will give us useful information on the role of histone chaperones in human physiology and human disease.