Mechanisms of tumor suppression by the chromatin deacetylase SIRT6

描述(申请人提供)：染色体稳定性丧失是人类癌症的常见特征。细胞如何维持染色体的完整性尚不完全清楚；然而，很明显，这涉及许多途径和蛋白质复合体。维持正确的染色体含量(整倍体)是维持染色体整体稳定的重要因素。新的数据表明，近着丝粒重复DNA元件的表观遗传沉默在维持整倍体方面起着关键作用。有缺陷的着丝粒周围沉默足以导致染色体不稳定，并在动物模型中导致恶性。这一应用主要关注sirtuin SIRT6在肿瘤抑制、着丝粒周围沉默和倍性维持中的新功能。Sirtuins是一个蛋白脱乙酰酶家族，可以促进哺乳动物许多方面的健康，其中包括抑制肿瘤。该实验室的长期目标是阐明sirtuins，特别是SIRT6，促进健康寿命的机制。申请人的实验室最近发表的研究表明，SIRT6在人类和小鼠中作为肠道肿瘤抑制因子发挥作用，至少部分是通过减弱MYC和HIF1信号。这项应用的目的是阐明SIRT6在肿瘤抑制中的第三个作用，特别是在着丝粒周围沉默和染色体稳定方面。这一应用的中心假设是SIRT6促进着丝粒周围DNA的表观遗传沉默，以促进整倍体的维持，这一功能有助于其肿瘤抑制功能。这些研究的基本原理是，对SIRT6、着丝粒周围沉默和整倍体之间的关系进行机械性剖析将有助于增强对染色体稳定性的整体理解。这项工作将以三个具体目标进行。首先，阐明SIRT6‘S与已知染色质沉默因子相互作用的意义。SIRT6缺陷细胞中潜在的有丝分裂缺陷将通过活细胞成像来识别。其次，将评估SIRT6功能丧失对肠道上皮细胞和腺瘤恶性特性和非整倍体诱导的影响。第三，SIRT6过表达抑制腺瘤病的能力将在体内进行测试。这种方法是创新的，因为对着丝点周围沉默对倍性维持的贡献仍然不完全清楚，SIRT6以前没有与这一过程联系在一起。这项工作意义重大，因为它可能为倍性维持机制提供新的见解，而倍性维持机制反过来又是总体基因组稳定和肿瘤抑制的主要因素。

DESCRIPTION (provided by applicant): Loss of chromosomal stability is a common feature of human carcinomas. How cells maintain chromosomal integrity is incompletely understood; however it is clear that many pathways and protein complexes are involved. Maintenance of the correct chromosomal content (euploidy) is an important contributor to overall chromosomal stability. Emerging data indicate that epigenetic silencing of pericentromeric repetitive DNA elements plays a key role in maintenance of euploidy. Defective pericentromeric silencing is sufficient to induce chromosomal instability and, in animal models, malignancy. This application focuses on novel functions for the sirtuin SIRT6 in tumor suppression, pericentromeric silencing, and ploidy maintenance. The sirtuins are a family of protein deacetylases that promote many aspects of healthspan in mammals, among them tumor suppression. The long- term goal of the laboratory is to elucidate mechanisms by which sirtuins, in particular SIRT6, promote healthspan. Recently published work by the applicant's laboratory has shown that SIRT6 functions as an intestinal tumor suppressor in humans and mice, at least in part via attenuation of MYC and HIF1 signaling. The objective of this application is to elucidate a third role of SIRT6 in tumor suppression, specifically in pericentromeric silencing and chromosomal stability. The central hypothesis of this application is that SIRT6 promotes epigenetic silencing of pericentromeric DNA to promote euploidy maintenance, a function that contributes to its tumor suppressor function. The rationale for these studies is that a mechanistic dissection of the relationships between SIRT6, pericentromeric silencing, and euploidy will contribute to an enhanced understanding of chromosomal stability overall. This work will be carried out in three Specific Aims. First, the significance of SIRT6's interactions with known chromatin silencing factors will be elucidated. Potential mitotic defects in SIRT6-deficient cells will be identified b live-cell imaging. Second, the impact of loss of SIRT6 function will be assessed in intestinal epithelial cells and adenomas with respect to malignant properties and induction of aneuploidy. Third, the ability of SIRT6 overexpression to suppress adenomatosis will be tested in vivo. The approach is innovative, in that the contribution of pericentromeric silencing to ploidy maintenance is still incompletely understood, and SIRT6 has not previously been linked to this process. The work is significant, in that it is likely to provide new insights into mechanisms of ploidy maintenance, which in turn is a major factor in overall genomic stability and tumor suppression.