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转运因子和组蛋白伴侣的功能如何协调，并调节组蛋白在特定染色质结构域的组装。我们将确定组蛋白伴侣如何支配组蛋白在细胞中的运动，从而作为组蛋白功能的一般调节者。每一个细胞周期，细胞的全部DNA内容都被迅速复制，并用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。组蛋白是由核丝蛋白家族的特定成员导入细胞核的。组蛋白伴侣也是组蛋白代谢的关键参与者，在组蛋白合成后不久结合组蛋白并护送它们到核小体。本项目重点关注组蛋白伴侣在组蛋白输入和输出中的作用，以及组蛋白伴侣是否调节组蛋白在细胞内的运动这一重要问题。该项目建立在先前的观察基础上，酵母组蛋白伴侣蛋白nap1p是组蛋白核输入因子。具体来说，我们将检验H3和H4的特异性组蛋白伴侣蛋白，如Asflp，调控组蛋白核的进出口的假设。假设组蛋白伴侣Naplp作为H2A。并调控H2A的细胞定位。Z将被测试。最后，我们将验证这一假设，即不同的可逆磷酸化事件调节着Naplp的功能周期，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调控的机制。核小体的正确组装对于维持所有细胞的基因组稳定性至关重要。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一致。这突出了在酵母中剖析组蛋白伴侣蛋白作为模式生物的功能的重要性，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.