Studies on ROC1-dependent E3 ubiquitin ligases

描述(申请人提供)：在细胞中，大多数不需要的和有害的蛋白质通过一种称为泛素-蛋白酶体途径的过程被消除。在这个过程中，目标蛋白被标记上一系列泛素分子，然后产生的标记蛋白被蛋白酶体识别，从而驱动蛋白质降解。泛素标记和蛋白酶体活性的正常运行对细胞和生物体的功能至关重要。泛素-蛋白酶体系统的调节缺陷在包括癌症在内的人类疾病中都很明显。我们的长期目标是了解SCF E3泛素连接酶复合体的精确功能，它是细胞中负责将大量蛋白质标记为泛素链以进行降解的关键机制。我们项目的短期目标是确定泛素链是如何建立在蛋白质上的，蛋白质是降解的信号。蛋白质靶标有一个内置的“降解代码”，指示它被摧毁。在泛素分子中，存在指导形成泛素链或连接泛素与蛋白质靶标的连接的“连接密码”。泛素标记反应可以看作是一个过程，开始于通过包括SCF E3和UbcH5和CDC34等酶在内的蛋白质促进剂“读取”蛋白质靶标上的“降解密码”和泛素“连接密码”。随后，SCF、UbcH5和CDC34作用于“建立”一个大的蛋白质网络，该网络将蛋白质靶标与泛素链连接起来。然而，关于泛素“结合密码”的性质、如何“阅读”这些密码，以及泛素标记所需的网络“构建”过程，人们仍然知之甚少。利用生物化学、分子生物学和细胞生物学的工具，我们的项目是：1)识别新的分子成分，帮助形成蛋白质靶标和触发泛素标记过程的SCF E3的复合体；2)了解SCF、UbcH5和CDc34如何建立蛋白质网络，用泛素标记目标蛋白质；3)识别泛素“连接密码”，并揭开CDC34如何阅读这些“密码”的谜团。

DESCRIPTION (provided by applicant): In cells, a majority of unwanted and harmful proteins are eliminated through a process called the ubiquitin-proteasome pathway. In this process, a target protein is tagged with a chain of ubiquitin molecules and the resulting marked protein is then recognized by the proteasome, which drives protein degradation. Proper functioning of the ubiquitin tagging and proteasomal activities is of key importance for the function of a cell and an organism. Defective regulation of the ubiquitin-proteasome system is manifest in human diseases including cancers. Our long-range goal is to understand the precise functioning of the SCF E3 ubiquitin ligase complex, which is the key machinery in cells responsible for tagging a large set of proteins with a chain of ubiquitin for degradation. The short-term objective of our project is to determine how a chain of ubiquitin is built on a protein, which signals degradation. A protein target has a built-in "degradation code" that dictates its destruction. In an ubiquitin molecule, "conjugation codes" are present to direct the formation of an ubiquitin chain, or a linkage that connects an ubiquitin to the protein target. The ubiquitin tagging reaction can be viewed as a process, beginning with the "reading" of the "degradation code" on the protein target, and ubiquitin "conjugation codes," by protein facilitators that include SCF E3 and enzymes such as UbcH5 and Cdc34. Subsequently, SCF, UbcH5, and Cdc34 act to "build" a large protein network that links the protein target with a chain of ubiquitin. However, it remains poorly understood regarding the nature of the ubiquitin "conjugation codes," how these codes are "read," as well as the network "building" process necessary for ubiquitin tagging. Using the tools of biochemistry, molecular biology and cell biology, our project is to: 1) identify new molecular components that help form the complex of a protein target and an SCF E3, which triggers the ubiquitin tagging process; 2) understand how SCF, UbcH5, and Cdc34 build protein networks for tagging a target protein with ubiquitin; 3) identify the ubiquitin "conjugation codes" and uncover the mystery of how Cdc34 reads these "codes."