SIRT7在肿瘤发生发展中的研究进展

Sirtuins蛋白家族是一类高度保守的烟酰胺腺嘌呤二核苷酸(NAD+)依赖的组蛋白去乙酰化酶。哺乳动物中的Sirtuins包括七种亚型:SIRT1-SIRT7,作为Sirtuins蛋白家族成员之一,SIRT7定位于核仁,是一种高度特异性的H3K18Ac(组蛋白H3的乙酰化赖氨酸残基18)去乙酰化酶。SIRT7的作用底物包括组蛋白和非组蛋白,底物的多样性决定着它参与体内多种细胞活动,如:细胞增殖、细胞新陈代谢、DNA损伤和应激反应等,并与肿瘤的发生发展密切相关。SIRT7在乳腺癌、甲状腺癌、卵巢癌、宫颈癌、胃癌、结直肠癌和肝细胞癌等多种肿瘤中高表达;而在头颈部鳞癌和胰腺癌中的低表达又提示其可作为抑癌基因发挥作用。本文旨从SIRT7的基因组组成、作用底物及相关肿瘤作用机制等方面阐述SIRT7的研究进展,而其致癌或抑癌作用有可能使其成为肿瘤治疗的新靶点。     

沉默信息调节因子3在神经退行性疾病中的作用CSCD

沉默信息调节因子3(silent information regulator 3,SIRT3)是一种NAD+依赖性Ⅲ类组蛋白去乙酰化酶,在代谢活跃的组织中高表达,如肾脏、心肌、棕色脂肪、脑等。越来越多的研究表明,SIRT3通过对组蛋白以及多种非组蛋白的去乙酰化,在能量代谢、肿瘤、衰老等过程中起到了重要作用。近年研究发现,在神经退行性疾病中,SIRT3激活可以减缓或者抑制线粒体功能障碍,从而表现出了明显的神经保护作用。本文对SIRT3在神经退行性疾病中的保护作用及其可能机制作一综述。     

沉默信息调节因子3在神经退行性疾病中的作用

沉默信息调节因子3(silent information regulator 3,SIRT3)是一种NAD+依赖性Ⅲ类组蛋白去乙酰化酶,在代谢活跃的组织中高表达,如肾脏、心肌、棕色脂肪、脑等。越来越多的研究表明,SIRT3通过对组蛋白以及多种非组蛋白的去乙酰化,在能量代谢、肿瘤、衰老等过程中起到了重要作用。近年研究发现,在神经退行性疾病中,SIRT3激活可以减缓或者抑制线粒体功能障碍,从而表现出了明显的神经保护作用。本文对SIRT3在神经退行性疾病中的保护作用及其可能机制作一综述。     

SIRT3在心血管疾病中的作用

沉默信息调节因子2相关酶类3(silent mating type information regulation2 homolog-3,SIRT3)是一种依赖于烟酰胺腺嘌呤二核苷酸(nicotinamide-adenine dinucleotide,NAD)的III类去乙酰化酶。SIRT3主要定位于线粒体,广泛分布于肾脏、脑、心脏及肝脏等富含线粒体的组织器官中,其可对组蛋白和非组蛋白去乙酰化在调控细胞代谢、细胞周期、细胞凋亡及细胞寿命方面起着重要的作用。SIRT3通过去乙酰化相关靶蛋白调节其生物活性,在抵抗氧化应激反应,改善血管内皮细胞功能等多种心血管疾病中,都起到了保护性作用。该文旨在对SIRT3在常见的心血管疾病中的作用的研究进展进行综述。     

SIRT3与细胞代谢及心血管疾病的相关性

蛋白去乙酰化酶在细胞生理过程中发挥着极为重要的作用。人蛋白去乙酰化酶包括HDACⅠ、HDACⅡ、HDACⅢ和HDACⅣ4个家族。其中第Ⅲ类即Sir2(Silent information regulator 2)家族包括7个成员——SIRT1~ SIRT7,每个成员都具有不同的细胞定位,并且发挥不同的生物学功能。作为主要定位于线粒体的组蛋白去乙酰化酶,SIRT3不仅调节细胞的能量代谢,并在细胞凋亡、肿瘤生长和一些疾病中发挥作用。文章综述了SIRT3在细胞代谢中的生物学功能以及其在心血管疾病中的研究进展。     

SIRT6与心血管、肿瘤及代谢性疾病

SIRT6是酵母Sir2在哺乳动物中的同源物Sirtuins家族SIRT1-SIRT7中的一员,主要存在于细胞核中,具有组蛋白去乙酰化酶及ADP-核糖基转移酶活性。人类SIRT6在其生理、病理过程中具有重要作用,参与机体生长、发育、代谢及炎症反应等过程。最新研究发现,SIRT6还涉及多种重大疾病的发生和发展。本文将从SIRT6与心血管、肿瘤、代谢等相关疾病的关系作一介绍,揭示了SIRT6与相关疾病的内在联系。     

去乙酰化酶SIRT1对氧化应激的调控

去乙酰化酶SIRT1在许多生物过程中具有重要的作用,包括氧化应激、能量代谢、细胞分化及基因组稳定等。细胞的存活及其寿命和氧化应激的存在密切相关。氧化应激可引起多种病理表现,如内皮损伤、线粒体损伤、炎症、自噬、凋亡甚至坏死等。近来研究发现,SIRT1在多种氧化应激相关疾病中保护细胞存活。SIRT1可以通过调控不同转录因子而发挥抗氧化应激作用,但研究发现,SIRT1也对氧化应激有负性调控作用。本文就SIRT1对氧化应激的调控进行概述。     

Sirtuins家族在DNA损伤修复中的作用

Sirtuins家族蛋白是一类依赖NAD的去乙酰化酶,属于第Ш类去乙酰化酶(HDACs),哺乳动物Sirtuins家族成员共有7个(SIRT1-7),其主要具有去乙酰化酶的活性,可以使多种蛋白发生去乙酰化,进而参与DNA的损伤修复、基因的转录调控、细胞凋亡、代谢及衰老等诸多生物进程。本文主要对Sirtuins家族在DNA损伤修复中的作用及其相关机制进行阐述。     

组蛋白去乙酰化酶SIRT7研究进展

SIRT7是哺乳动物组蛋白去乙酰化酶Sirtuins家族成员,是高度保守的NAD+依赖的蛋白质去乙酰化酶,调控细胞中多种蛋白的乙酰化水平,参与许多重要的生命活动,如蛋白质合成、代谢、细胞应激、炎症、衰老和肿瘤.在过去的几年里,人们对它的认识有质的飞跃,本文主要对SIRT7的特点、功能和调节机制进行回顾和总结,以期为进一步研究提供参考.     

含有多种酶活性的SIRT5蛋白在细胞代谢中的功能

Sirtuins作为Ⅲ型蛋白质去乙酰化酶调控机体多种生理进程,包括DNA修复、基因组稳定性、能量代谢、衰老以及癌症发生.目前已鉴定出7种人类Sirtuins家族的蛋白(SIRT1–SIRT7),其组织分布、亚细胞定位以及酶作用的底物都不尽相同.本文将着重描述Sirtuins家族的一个成员—SIRT5以及其在调控细胞代谢中的多种酶活性.     

SIRT1 coordinates with the CRL4B complex to regulate pancreatic cancer stem cells to promote tumorigenesis

Pancreatic cancer is a common malignant tumor with poor prognosis. Recently, cancer stem cells (CSCs) were identified in several solid tumors, including pancreatic cancer. Although accumulating evidence indicates that sirtuin 1 (SIRT1) exerts biological functions in various cancers, how it contributes to tumorigenesis and metastasis of pancreatic cancer, as well as its role in CSCs, is still poorly defined. Here we show that SIRT1 interacts with the Cullin 4B (CUL4B)-Ring E3 ligase (CRL4B) complex, which is responsible for H2AK119 monoubiquitination (H2AK119ub1), collaborating as a functional unit. Genome-wide analysis of SIRT1/CUL4B targets identified a cohort of genes, including GRHL3 and FOXO3, critically involved in cell differentiation, growth, and migration. Furthermore, we found that SIRT1 and CUL4B collectively promote the proliferation, autophagy, and invasion of pancreatic cancer cells. Remarkably, we demonstrate that SIRT1/CUL4B promotes CSC-like properties, including increased stemness marker expression and sphere formation. In vivo experiments implied that SIRT1 promoted established tumor xenograft growth, increased tumor-initiating capacity in NOD/SCID mice, and increased CSC frequency. Strikingly, SIRT1 and CUL4B expression is markedly upregulated in a variety of human cancers, including pancreatic cancer. Our data provide a molecular basis for the functional interplay between histone deacetylation and ubiquitination. The results also implicate the SIRT1/CRL4B complex in pancreatic cancer metastasis and stem cell properties, thus supporting SIRT1 as a promising potential target for cancer therapy development.Subject terms: Cancer stem cells, Metastasis     

SIRT7 promotes chromosome synapsis during prophase I of female meiosis

Sirtuins are NAD⁺-dependent protein deacylases and ADP-ribosyltransferases that are involved in a wide range of cellular processes including genome homeostasis and metabolism. Sirtuins are expressed in human and mouse oocytes yet their role during female gamete development are not fully understood. Here, we investigated the role of a mammalian sirtuin member, SIRT7, in oocytes using a mouse knockout (KO) model. Sirt7 KO females have compromised fecundity characterized by a rapid fertility decline with age, suggesting the existence of a diminished oocyte pool. Accordingly, Sirt7 KO females produced fewer oocytes and ovulated fewer eggs. Because of the documented role of SIRT7 in DNA repair, we investigated whether SIRT7 regulates prophase I when meiotic recombination occurs. Sirt7 KO pachynema-like staged oocytes had approximately twofold increased γH2AX signals associated with regions with unsynapsed chromosomes. Consistent with the presence of asynaptic chromosome regions, Sirt7 KO oocytes had fewer MLH1 foci (~one less), a mark of crossover-mediated repair, than WT oocytes. Moreover, this reduced level of crossing over is consistent with an observed twofold increased incidence of aneuploidy in Metaphase II eggs. In addition, we found that acetylated lysine 18 of histone H3 (H3K18ac), an established SIRT7 substrate, was increased at asynaptic chromosome regions suggesting a functional relationship between this epigenetic mark and chromosome synapsis. Taken together, our findings demonstrate a pivotal role for SIRT7 in oocyte meiosis by promoting chromosome synapsis and have unveiled the importance of SIRT7 as novel regulator of the reproductive lifespan.

     

SIRT7琥珀酰化修饰对肝癌生存、免疫浸润及预后的相关性分析

摘要 目的：探究SIRT7基因琥珀酰化修饰对肝癌患者的生存、免疫浸润及预后的相关性分析。方法：采用生物信息分析法对SIRT7在肝癌组织中的表达情况及其对肝癌患者预后的影响进行分析；采用蛋白免疫印迹法（Western blot）检测其转染效果。结果：（1）生物信息分析结果显示：SIRT7在多种肿瘤（包括肝癌）组织中呈高表达（P<0.05）；SIRT7的表达与肿瘤的生存曲线相关（P<0.05）；肝癌患者的SIRT7相对表达量与其预后相关，高表达组肝癌患者的总生存情况（P=0.017）和无进展生存情况较低表达组缩短（P=0.004）；免疫浸润和肿瘤微环境分析结果显示，SIRT7表达水平与多数免疫细胞浸润水平、肿瘤微环境(ESTIMATES core)均有明显负相关。（2）Western blot显示，SIRT7在肝癌细胞中表达高于正常细胞。因此，SIRT7 可作为肝癌的潜在预后标志物。结论：SIRT7表达水平与肝癌(HCC)患者的预后、免疫细胞浸润性、肿瘤微环境免疫细胞和基质细胞浸润等相关。     

SIRT1 and c-Myc Promote Liver Tumor Cell Survival and Predict Poor Survival of Human Hepatocellular Carcinomas

The increased expression of SIRT1 has recently been identified in numerous human tumors and a possible correlation with c-Myc oncogene has been proposed. However, it remains unclear whether SIRT1 functions as an oncogene or tumor suppressor. We sought to elucidate the role of SIRT1 in liver cancer under the influence of c-Myc and to determine the prognostic significance of SIRT1 and c-Myc expression in human hepatocellular carcinoma. The effect of either over-expression or knock down of SIRT1 on cell proliferation and survival was evaluated in both mouse and human liver cancer cells. Nicotinamide, an inhibitor of SIRT1, was also evaluated for its effects on liver tumorigenesis. The prognostic significance of the immunohistochemical detection of SIRT1 and c-Myc was evaluated in 154 hepatocellular carcinoma patients. SIRT1 and c-Myc regulate each other via a positive feedback loop and act synergistically to promote hepatocellular proliferation in both mice and human liver tumor cells. Tumor growth was significantly inhibited by nicotinamide in vivo and in vitro. In human hepatocellular carcinoma, SIRT1 expression positively correlated with c-Myc, Ki67 and p53 expression, as well as high á-fetoprotein level. Moreover, the expression of SIRT1, c-Myc and p53 were independent prognostic indicators of hepatocellular carcinoma. In conclusion, this study demonstrates that SIRT1 expression supports liver tumorigenesis and is closely correlated with oncogenic c-MYC expression. In addition, both SIRT1 and c-Myc may be useful prognostic indicators of hepatocellular carcinoma and SIRT1 targeted therapy may be beneficial in the treatment of hepatocellular carcinoma.     

SIRT1 inhibits transforming growth factor beta-induced apoptosis in glomerular mesangial cells via Smad7 deacetylation

SIRT1, a class III histone deacetylase, is considered a key regulator of cell survival and apoptosis through its interaction with nuclear proteins. In this study, we have examined the likelihood and role of the interaction between SIRT1 and Smad7, which mediates transforming growth factor beta (TGFbeta)-induced apoptosis in renal glomerular mesangial cells. Immunoprecipitation analysis revealed that SIRT1 directly interacts with the N terminus of Smad7. Furthermore, SIRT1 reversed acetyl-transferase (p300)-mediated acetylation of two lysine residues (Lys-64 and -70) on Smad7. In mesangial cells, the Smad7 expression level was reduced by SIRT1 overexpression and increased by SIRT1 knockdown. SIRT1-mediated deacetylation of Smad7 enhanced Smad ubiquitination regulatory factor 1 (Smurf1)-mediated ubiquitin proteasome degradation, which contributed to the low expression of Smad7 in SIRT1-overexpressing mesangial cells. Stimulation by TGFbeta or overexpression of Smad7 induced mesangial cell apoptosis, as assessed by morphological apoptotic changes (nuclear condensation) and biological apoptotic markers (cleavages of caspase3 and poly(ADP-ribose) polymerase). However, TGFbeta failed to induce apoptosis in Smad7 knockdown mesangial cells, indicating that Smad7 mainly mediates TGFbeta-induced apoptosis of mesangial cells. Finally, SIRT1 overexpression attenuated both Smad7- and TGFbeta-induced mesangial cell apoptosis, whereas SIRT1 knockdown enhanced this apoptosis. We have concluded that Smad7 is a new target molecule for SIRT1 and SIRT1 attenuates TGFbeta-induced mesangial cell apoptosis through acceleration of Smad7 degradation. Our results suggest that up-regulation of SIRT1 deacetylase activity is a potentially useful therapeutic strategy for prevention of TGFbeta-related kidney disease through its effect on cell survival.     

SIRT3 Enhances Glycolysis and Proliferation in SIRT3-Expressing Gastric Cancer Cells

SIRT3 is a key NAD⁺-dependent protein deacetylase in the mitochondria of mammalian cells, functioning to prevent cell aging and transformation via regulation of mitochondrial metabolic homeostasis. However, SIRT3 is also found to express in some human tumors; its role in these SIRT3-expressing tumor cells needs to be elucidated. This study demonstrated that the expression of SIRT3 was elevated in a group of gastric cancer cells compared to normal gastric epithelial cells. Although SIRT3 expression levels were increased in the gastric tumor tissues compared to the adjacent non-tumor tissues, SIRT3 positive cancer cells were more frequently detected in the intestinal type gastric cancers than the diffuse type gastric cancers, indicating that SIRT3 is linked with subtypes of gastric cancer. Overexpression of SIRT3 promoted cell proliferation and enhanced ATP generation, glucose uptake, glycogen formation, MnSOD activity and lactate production, which were inhibited by SIRT3 knockdown, indicating that SIRT3 plays a role in reprogramming the bioenergetics in gastric tumor cells. Further analysis revealed that SIRT3 interacted with and deacetylated the lactate dehydrogenase A (LDHA), a key protein in regulating anaerobic glycolysis, enhancing LDHA activity. In consistence, a cluster of glycolysis-associated genes was upregulated in the SIRT3-overexpressing gastric tumor cells. Thus, in addition to the well-documented SIRT3-mediated mitochondrial homeostasis in normal cells, SIRT3 may enhance glycolysis and cell proliferation in SIRT3-expressing cancer cells.