Ubiquitin-mediated protein degradation as a mechanism to control the DNA replication and DNA damage checkpoints in the mammalian cell cycle

泛素通路通过控制关键细胞周期蛋白的丰度，在细胞生长和细胞增殖调控中起着核心作用。越来越多的证据表明，许多细胞周期调节因子的非预定蛋白水解对肿瘤发生有重要作用，并且确实在许多类型的人类癌症中发现，例如结肠癌和肾细胞癌以及非霍奇金淋巴瘤。蛋白质降解途径也是癌症治疗的靶点，如成功引入硼替佐米（一种26S蛋白酶体抑制剂）所示。因此，这一领域的进一步工作对理解和治疗多种癌症具有很大的希望。Pagano博士在纽约大学癌症中心的实验室对泛素介导的蛋白质水解的理解做出了重大贡献，并对控制哺乳动物细胞周期的两种主要泛素连接酶产生了基本的见解：SCF （Skp1 Cul1 F-box）和APC/C（后期促进复合物/环体）泛素连接酶家族。在基于质谱的SCF新底物筛选中，发现了与哺乳动物细胞周期DNA复制和DNA损伤检查点调控的潜在联系。这种联系源于DNA复制检查点分子Claspin作为潜在SCF底物的鉴定。该研究的目的是描述基于SCF的泛素化对哺乳动物DNA复制和DNA损伤检查点的调节的机制，以及该机制的解除管制如何参与肿瘤发生。

The ubiquitin pathway plays a central role in the regulation of cell growth and cell proliferation by controlling the abundance of key cell cycle proteins. Increasing evidence indicates that unscheduled proteolysis of many cell cycle regulators contributes significantly to tumorigenesis and is indeed found in many types of human cancers, for example colon and renal cell cancer and non hodgkin lymphomas. Protein degradation pathways are also targets for cancer therapy, as shown by the successful introduction of bortezomib, an inhibitor of the 26S proteasome. Thus, further work in this area holds great promise toward the understanding and treatment of a wide range of cancers. The laboratory of Dr. Pagano at the NYU Cancer Center has significantly contributed to the understanding of ubiquitin mediated proteolysis and generated fundamental insights into the two major ubiquitin ligases in control of the mammallian cell cycle: The SCF (Skp1 Cul1 F-box) and APC/C (Anaphase Promoting Complex/Cyclosome) family of ubiquitin ligases. In a mass spectrometry based screen for novel substrates of the SCF, a potential link to the regulation of the DNA replication and DNA damage checkpoints of the mammalian cell cycle was found. This connection stems from the identification of the DNA replication checkpoint molecule Claspin as a potential SCF substrate. It is the aim of the proposed research fellowship to characterize the mechanism by which SCF based ubiquitination contributes to the regulation of mammalian DNA replication and DNA damage checkpoints and how deregulation of this mechanism may be involved in tumorigenesis.