Role of the ubiquitin system in epigenetic regulation

泛素是一种由76个氨基酸组成的小蛋白，从酵母到人类都保存得很好。它可以通过一种称为泛素化的过程共价添加到数千种不同的蛋白质上，为细胞调节提供多样性和动力学。组蛋白是一组基本的核蛋白，它将线性DNA结合并组织成称为核小体的结构单位，核小体进一步浓缩成染色质。组蛋白的泛素修饰直接参与许多重要的细胞功能，包括转录、DNA复制、修复和基因沉默，因此在细胞分裂、生长和分化的调节中起着关键作用。这种组蛋白修饰的机制和参与这一过程的玩家还没有得到很好的描述。我们的研究计划的目标是了解组蛋白泛素修饰在细胞调控中的机制和重要性。*在这一应用中，我们将重点阐明参与组蛋白H2A泛素化的泛素系统。H_2A泛素化参与了干细胞基因组完整性的维持、发育模式的形成、X染色体的失活和多能性的维持。负责H_2A泛素化的蛋白质包括一系列酶，E1(活化酶)、E_2(结合酶)和E3(连接酶)，它们将泛素共价连接到H_2A的特定赖氨酸残基上。通过蛋白质组学、生物化学和细胞学的方法，我们建议描述H_2A泛素化的机制，揭示每个蛋白质参与者在这一过程中的作用，并了解H_2A泛素化在细胞调节中的作用。具体目标包括：(1)揭示体内和体外H_2A泛素化所需的特定酶；(2)表征H_2A泛素化的分子基础以及这些酶在基因调控中的作用；(3)研究导致H_2A变异体泛素化的特定酶。通过研究这些酶是如何工作的，我们将更好地理解组蛋白泛素化的重要性，以及它如何参与不同生物过程中基因表达的调控。

Ubiquitin, a 76 amino acid small protein, is well conserved from yeast to humans. It can be covalently added onto thousands of different proteins through a process known as ubiquitination to provide diversity and dynamics to cell regulation. Histones are a group of basic nuclear proteins that bind and organize the linear DNA into the structural units called nucleosomes, which are further condensed into chromatin. Ubiquitin modification of histones is directly involved in many vital cellular functions including transcription, DNA replication, repair and gene silencing and therefore plays a critical role in the regulation of cell division, growth and differentiation. The mechanism of this histone modification and the players involved in this process are poorly characterized. The goal of our research program is to understand the mechanism and the importance of ubiquitin modification of histones in cellular regulation.***In this application, we will focus on elucidation of the ubiquitin system involved in ubiquitination of histone H2A. H2A ubiquitination is involved in the maintenance of genome integrity, developmental patterning, X-chromosome inactivation and maintenance of pluripotency of stem cells. The proteins responsible for H2A ubiquitination include a cascade of enzymes, E1 (activating enzyme), E2 (conjugating enzymes) and E3 (ligases), which covalently attaching ubiquitin to specific lysine residues of H2A. Through proteomic, biochemical and cellular approaches, we propose to characterize the mechanism of H2A ubiquitination, to reveal the roles of each protein player in this process and to understand the function of H2A ubiquitination in cellular regulation. Specific aims include: (1) to reveal specific enzymes required for H2A ubiquitination in vitro and in vivo; (2) to characterize the molecular basis of H2A ubiquitination and the roles of these enzymes in gene regulation; and (3) to investigate specific enzymes that are responsible for ubiquitination of the H2A variants. By studying how these enzymes work, we will gain a better understanding of the importance of histone ubiquitination and how it is involved in the regulation of gene expression in different biological processes.