Studies of the Smc5/Smc6 complex in chromosomal replication

描述（申请人提供）：癌症和其他人类疾病中出现的许多染色体异常和遗传不稳定都是由染色体复制缺陷引起的。染色体复制不仅需要基本复制机制的正常功能，还需要能够应对染色质的复杂性质和模板上的病变，这两者都可能导致复制叉停滞或崩溃。检查点通路已被证明在介导促进复制恢复和完成的多种措施中发挥关键作用。此外，能够协调染色体行为和基本DNA复制程序的特殊机制至关重要。SMC （structural maintenance of chromosome）蛋白及其复合体，包括新近发现的Smc5/6复合体，是一种动态的分子连接体，能够主动地拴住和折叠染色单体，从而在染色体结构和复制程序之间提供重要的联系。我们的长期目标是了解染色体复制中使用的特殊程序。在本次授权期内，我们将重点研究Smc5/6复合体在复制中的功能。我们发现Smc5/6复合体在染色体复制中发挥多种作用，其中一些作用是由其SUMO E3亚基Mms21介导的。利用遗传学、细胞生物学和生化方法的结合，我们将研究Smc5/6复合体调节染色体复制的机制。在具体目标一中，我们将确定Smc5/6复合体如何在受损的复制分叉处抵消重组事件。在具体目标二中，我们将研究Smc5/6复合体在复制中的其他功能，并探索Smc5/6复合体与重要复制蛋白之间的物理相互作用。这两个目标的综合结果将为复制、染色体动力学和重组修复之间的关系提供新的见解。它可能有助于了解人类Smc5/6复合物的功能，并可能导致对抗与癌症和其他人类疾病相关的基因组不稳定性的方法。由于染色质和核组织的复杂性，染色体复制面临着许多挑战。因此，它需要特殊的机制来协调染色体行为和基本的DNA复制和修复程序。进化上保守的Smc5/6复合体在这些过程的界面上起作用。我们描述的研究方案，以解决机制，通过这种复杂的共同调节不同途径在染色体复制。这些研究的结果将为这些基本过程提供新的见解，并将阐明与这些过程中的缺陷相关的人类疾病的原因和治疗。

DESCRIPTION (provided by applicant): Many chromosomal abnormalities and genetic instability arising in cancer and other human diseases are caused by defects in chromosomal replication. Chromosomal replication not only requires the proper function of the basic replication machinery, but also demands an ability to cope with the complex nature of chromatin and lesions on the template, both of which can lead to replication fork stalling or collapse. Checkpoint pathways have been shown to play key roles in mediating multiple measures that promote the recovery and completion of replication. In addition, special mechanisms that can coordinate chromosomal behavior and basic DNA replication programs are critical. SMC (structural maintenance of chromosome) proteins and their complexes, including the newly characterized Smc5/6 complex, are dynamic molecular linkers that can actively tether and fold chromatids, thereby providing important connections between chromosomal structures and replication programs. Our long-term goal is to understand the special programs utilized in chromosomal replication. In this grant period, we will focus on functions of the Smc5/6 complex in replication. We showed that the Smc5/6 complex plays multiple roles in chromosomal replication and some of its roles are mediated by its SUMO E3 subunit Mms21. Using a combination of genetic, cell biological, and biochemical approaches, we will study the mechanisms by which the Smc5/6 complex regulates chromosomal replication. In specific aim one, we will determine how the Smc5/6 complex counteracts recombinogenic events at damaged replication forks. In specific aim two, we will study the additional functions of the Smc5/6 complex in replication and probe for physical interactions between the Smc5/6 complex and proteins important for replication. The combined results from these two aims will provide new insights into the relationship between replication, chromosomal dynamics and recombinational repair. It will likely contribute to the understanding of the functions of the human Smc5/6 complex and potentially lead to methods to battle genomic instability associated with cancer and other human diseases. Chromosomal replication faces many challenges posed by the complex nature of chromatin and nuclear organization. It therefore requires special mechanisms that coordinate chromosomal behavior and basic DNA replication and repair programs. The evolutionarily conserved Smc5/6 complex functions at the interface of these processes. We describe research programs to address the mechanisms by which this complex co- regulates different pathways during chromosomal replication. Results from these studies will provide new insights into these fundamental processes and will shed lights on the cause and treatment of human diseases related to defects in these processes.