Mechanisms of tumor suppression by the chromatin deacetylase SIRT6

描述（由申请人提供）：染色体稳定性丧失是人类癌症的共同特征。细胞如何维持染色体的完整性尚不完全清楚；然而，很明显，许多途径和蛋白质复合物参与其中。维持正确的染色体含量（整倍体）是染色体整体稳定性的重要因素。新出现的数据表明，表观遗传沉默在维持整倍体中起着关键作用。有缺陷的中心点周围沉默足以诱导染色体不稳定，并在动物模型中诱发恶性肿瘤。该应用主要关注SIRT6在肿瘤抑制、中心体周围沉默和倍性维持方面的新功能。sirtuins是一个蛋白质去乙酰化酶家族，促进哺乳动物健康的许多方面，其中包括肿瘤抑制。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，至少部分是通过抑制MYC和HIF1信号。本应用的目的是阐明SIRT6在肿瘤抑制中的第三个作用，特别是在中心点周围沉默和染色体稳定性方面。该应用的中心假设是SIRT6促进表观遗传沉默，促进整倍体维持，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、中心点周围沉默和整倍体之间关系的机制解剖将有助于提高对染色体稳定性的总体理解。这项工作将在三个具体目标下进行。首先，将阐明SIRT6与已知染色质沉默因子相互作用的意义。sirt6缺陷细胞的潜在有丝分裂缺陷将通过活细胞成像识别。其次，将在肠上皮细胞和腺瘤中评估SIRT6功能缺失对恶性性质和诱导非整倍体的影响。第三，体内测试SIRT6过表达抑制腺瘤病的能力。这种方法是创新的，因为人们仍然不完全了解中心点周围沉默对倍性维持的贡献，而且SIRT6以前没有与这一过程联系起来。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，而倍性维持又是整体基因组稳定性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.