核转录因子E2Fs家族研究进展

核转录因子E2Fs家族 (E2F转录因子 )是视网膜母细胞瘤相关基因 (RB/E2F)通路中调控细胞有丝分裂事件的重要因子 ,E2F是否进入核内发挥核转录因子作用取决于RB蛋白的磷酸化状态 ,E2F调控的下游基因分为激活与抑制两种方式 ,涉及细胞周期调控、生长与凋亡、增殖与分化等重要生命活动。E2F在细胞周期中的功能失调将导致细胞上述机能的改变并有可能与肿瘤发生有关 ,深入研究无疑将对完整阐述细胞周期调控及肿瘤发生机制乃至寻求新的肿瘤治疗靶点提供帮助。     

核转录因子E2Fs家族研究进展

核转录因子E2Fs家族(E2F转录因子)是视网膜母细胞瘤相关基因(RB／E2F)通路中调控细胞有丝分裂事件的重要因子，E2F是否进入核内发挥核转录因子作用取决于RB蛋白的磷酸化状态，E2F调控的下游基因分为激活与抑制两种方式，涉及细胞周期调控、生长与凋亡、增殖与分化等重要生命活动。E2F在细胞周期中的功能失调将导致细胞上述机能的改变并有可能与肿瘤发生有关，深入研究无疑将对完整阐述细胞周期调控及肿瘤发生机制乃至寻求新的肿瘤治疗靶点提供帮助。     

白藜芦醇-Sirt1 Foxo1调控通路对缺氧心肌细胞的保护作用

目的 研究白藜芦醇-Sirt1-Foxo1调控通路对缺氧心肌细胞的保护作用。方法 将大鼠心肌细胞株H9C2培养48 h后,随机分为5组,即20 μmol/L白藜芦醇(resveratrol,Res)干预组、二甲基亚砜（dimethyl sulfoxide,DMSO）对照组、40 mmol/L尼克酰胺（nicotinamide,Nam）干预组、Nam空白对照组及正常对照组。培养24 h后终止培养,用RT-PCR法和免疫细胞化学染色法检测Sirt1、Foxo1、p27、Bim mRNA及其蛋白表达水平的变化;用TUNEL法及流式细胞仪（flow cytometer,FCM）分析细胞凋亡和细胞周期。结果 20 μmol/L Res干预组可使Sirt1 mRNA及SIRT1蛋白表达的水平增加。Sirt1可通过抑制Foxo1 mRNA的转录活性而调节其下游基因p27及Bim的表达。SIRT1的高表达可使细胞周期延长,细胞凋亡减少。结论 Res干预可使SIRT1表达增加。Sirt1可能通过对Foxo1及其下游基因Bim、p27的调控,延长心肌细胞的细胞周期,减少其凋亡。     

SIRT1与糖尿病相关肿瘤的关系

糖尿病不仅增加肿瘤的患病风险,而且促进肿瘤的复发和转移.沉默信息调节因子1(SIRT1)是机体的能量感受器,具有调节糖、脂代谢,抑制慢性非特异性炎性反应,改善胰岛素抵抗等作用,其表达及活性异常参与了糖尿病及其并发症的发生.同时近期研究发现SIRT1也与肿瘤的发生、发展密切相关.通过去乙酰化调节机制SIRT1可调控大量转录因子及组蛋白的活性,从而参与染色质沉默、细胞凋亡、自噬途径及DNA损伤修复的调控,是联系细胞能量代谢与染色质结构的关键蛋白,因而可能是联系糖尿病及糖尿病相关肿瘤的重要中介.积极干预糖尿病患者中SIRT1信号途径异常,可能具有降低肿瘤风险的作用.     

YB-1蛋白与肿瘤

肿瘤是一种细胞周期性疾病。人类YB-1（Y box-binding protein-1）蛋白作为细胞周期重要的正向调控因子和肿瘤细胞化疗耐药调控因子，已逐渐成为国外肿瘤研究的热点。人类YB-1蛋白能特异地出现于肿瘤组织中，癌组织早期即出现人类YB-1蛋白的表达异常。作为DNA结合蛋白家族的成员之一的YB-1蛋白，通过捆绑Y-box序列5’-CTGATTGG-3’来调节多药耐药相关基因1（MDRI），DNA聚合酶α，表皮生长因子受体（EGFR），细胞周期蛋白cyclin A和cyclin B1等基因的表达。本文就其在人类肿瘤中的作用作一综述。     

SIRT1在支气管哮喘中的研究进展

正沉默信息调节因子2(Sirt2)是1986年Ivy等人在酵母菌中发现的和长寿相关的基因[1],后来发现在哺乳动物中也存在和Sirt2同源蛋白,命名为SIRT1-SIRT7,其中SIRT1和酵母的Sirt2同源性最高。SIRT1作为细胞内重要的调节因子,广泛分布于人类多种细胞的胞浆和胞核,参与调节炎症、细胞周期、衰老和凋亡、应激等重要生理过程。与多种肺部疾病的发生发展密切相关,例如慢性阻塞性肺疾     

p53调控网络及p53与砷中毒研究进展

p53是一种重要的转录因子,是细胞应激的关键调控分子之一,它可以对细胞受到的各种压力作出反应,通过转录或非转录途径诱导细胞周期阻滞,细胞凋亡、衰老,DNA修复和细胞代谢改变等不同反应.在人类50％以上的肿瘤组织中均发现了p53基因的突变或p53上下游调控信号的异常,因此认为,野生型p53 (wtp53)可以抑制肿瘤的发生,大量不同类型的肿瘤与p53功能的改变或缺失有密切关系[1-2].     

细胞周期调控因子在消化道肿瘤表达的研究进展

完整的细胞周期包括间期和有丝分裂期(M期),间期包括G1期、S期、G2期,细胞周期得以运行的机制在于一系列细胞周期素(cyclin)时相起伏的调控下,相应的周期素依赖性蛋白激酶( cyclin-dependend-kinase,Cdk)依次激活,驱动细胞由G0、G1、S、G2到M期.细胞周期主要有2个调定点:G1/S期、G2/M期.科学家已发现有几类调控因子在细胞周期中起着重要作用:第一类是对细胞分裂增殖有调控作用的细胞生长因子;第二类为细胞周期调控因子,又称内源性调节因子,是细胞内自己合成的蛋白质.细胞周期调控因子在细胞分裂增殖中发挥重要作用,异常表达致使肿瘤细胞过度分裂及增殖,导致肿瘤扩散及转移.细胞周期调控因子分2类:正调控因子(cyclin-Cdk)可促进细胞通过调定点,而负调控因子(Ckis)则可抑制细胞通过调定点.     

SIRT1与肿瘤的研究进展

肿瘤的发生与癌基因的过表达或者抑癌基因的低表达密切相关.Ⅲ型组蛋白脱乙酰酶SIRT1的基因表达和脱乙酰酶活性在肿瘤细胞中均发生上调,由此推测这些也许导致了肿瘤的发生.SIRT1也能够引起肿瘤抑制因子的脱乙酰化从而促进肿瘤发生.在肿瘤的发生、发展、各种特性维持中,SIRT1因其能够促进肿瘤细胞增殖、抑制凋亡、衰老等活性很可能扮演着重要角色.然而,另一方面,SIRT1也能够脱乙酰化肿瘤促进因子而起到抑制肿瘤作用.SIRT1在肿瘤的发生过程中扮演的角色存在争议.因此,对SIRT1进行进一步研究就显得尤为重要,而其作为肿瘤治疗靶点的可能性使得研究更具临床意义.     

核转录因子-κB对β-淀粉样肽25-35诱导下PC12细胞周期的影响

目的 探讨核转录因子κB(NF-κB)在β-淀粉样蛋白(Aβ25-35)肽段诱导的PC12细胞周期异常中的机制.方法 应用流式细胞仪检测技术及Western印迹方法,在Aβ25-35诱导PC12细胞凋亡过程中检测NF-κB的活性和细胞周期相关蛋白周期蛋白A(cyclin A)、周期蛋白D1(cyclin D1)、周期蛋白E(cyclin E)、周期蛋白依赖性激酶2(CKD2)、周期蛋白依赖性激酶4(CKD4)、周期蛋白依赖性激酶6(CKD6)表达量的变化.分别将PC12同步化于G0期和S期,再检测Aβ25-35诱导对上述指标的影响.抑制NF-κB活性后,进一步检测上述细胞周期相关蛋白在Aβ25-35诱导下的变化.结果 Aβ25-35诱导PC12细胞凋亡过程中NF-κB活性增加(P＜0.05),同时细胞周期相关蛋白量升高;细胞同步化于G0期,Aβ25-35处理PC12细胞,细胞凋亡率下降,NF-κB活性的增加和细胞周期相关蛋白量升高均受抑制;而同步化于S期,则细胞凋亡率、NF-κB活性的增加和细胞周期相关蛋白量升高均无显著性变化;Aβ25-35诱导PC12细胞凋亡过程中,抑制NF-κB活性则会引起细胞周期相关蛋白表达受抑制.结论 NF-κB主导了Aβ25-35诱导PC12细胞周期的异常变化,异常发生在G0期到G1期的过渡以及G1期到S期过渡,而不是S期到G2期以及G2期到M期的过渡.     

SIRT1与血管性疾病的研究进展

沉默信息调节因子2相关酶1 (SIRT1)是一种高度保守的NAD+依赖的第Ⅲ类组蛋白去乙酰化酶,主要通过翻译后修饰调节DNA损伤修复、氧化应激、炎症、细胞衰老、凋亡与增殖等,从而参与血管性疾病的发生发展.因此,SIRT1可能成为治疗血管性疾病的潜在靶点.本文主要对SIRT1的主要生理作用及其在动脉粥样硬化、高血压、肺动脉高压、糖尿病肾病及糖尿病视网膜病变等常见血管性疾病中的作用作一综述.     

Sirtuin 1 alleviates endoplasmic reticulum stress-mediated apoptosis of intestinal epithelial cells in ulcerative colitis

BACKGROUND Sirtuin 1(SIRT1) is a nicotinamide adenine dinucleotide(NAD~+)-dependent protein deacetylase that is involved in various diseases,including cancers,metabolic diseases,and inflammation-associated diseases.However,the role of SIRT1 in ulcerative colitis(UC) is still confusing.AIM To investigate the role of SIRT1 in intestinal epithelial cells(IECs) in UC and further explore the underlying mechanisms.METHODS We developed a coculture model using macrophages and Caco-2 cells.After treatment with the SIRT1 activator SRT1720 or inhibitor nicotinamide(NAM),the expression of occludin and zona occludens 1(ZO-1) was assessed by Western blot analysis.Annexin V-APC/7-AAD assays were performed to evaluate Caco-2 apoptosis.Dextran sodium sulfate(DSS)-induced colitis mice were exposed to SRT1720 or NAM for 7 d.Transferase-mediated dUTP nick-end labeling(TUNEL) assays were conducted to assess apoptosis in colon tissues.The expression levels of glucose-regulated protein 78(GRP78),CCAAT/enhancerbinding protein homologous protein(CHOP),caspase-12,caspase-9,and caspase-3 in Caco-2 cells and the colon tissues of treated mice were examined by quantitative real-time PCR and Western blot RESULTS SRT1720 treatment increased the protein levels of occludin and ZO-1 and inhibited Caco-2 apoptosis,whereas NAM administration caused the opposite effects.DSS-induced colitis mice treated with SRT1720 had a lower disease activity index(P 0.01),histological score(P 0.001),inflammatory cytokine levels(P 0.01),and apoptotic cell rate(P 0.01),while exposure to NAM caused the opposite effects.Moreover,SIRT1 activation reduced the expression levels of GRP78,CHOP,cleaved caspase-12,cleaved caspase-9,and cleaved caspase-3 in Caco-2 cells and the colon tissues of treated mice.CONCLUSION SIRT1 activation reduces apoptosis of IECs via the suppression of endoplasmic reticulum stress-mediated apoptosis-associated molecules CHOP and caspase-12 SIRT1 activation may be a potential therapeutic strategy for UC.     

Cyclin D1, E2F1 expression levels are associated with characteristics and prognosis of esophageal squamous cell carcinoma

SUMMARY. We performed a multi-institutional analysis of E2F1 and cyclin D1 expression in cases of esophageal squamous cell carcinoma (ESCC). Cyclin D1 and E2F1 are involved in the transition of cell cycle phases and associated with tumor progression. However, no previous studies have concurrently analyzed combined E2F1 and cyclin D1 expression. The purpose of this study was to clarify the relationship of E2F1 and cyclin D1 in ESCC. We studied 122 patients with primary ESCC who underwent surgical tumor resection. Immunohistochemical analyses were performed for E2F1 and cyclin D1. A statistical analysis of immunohistochemistry results, clinicopathological features, and prognosis was performed. E2F1/cyclin D1 (-/-) tumors were present in 31 patients (25.4%) and correlated with reduced tumor progression. In these patients, pT (P=0.0001), pN (P<0.0001), p-Stage (P=0.0019), and survival rates were better than in patients who were positive for either E2F1 or cyclin D1 (P=0.0232). The expression of E2F1 and cyclin D1 is an indicator of tumor progression and prognosis in patients with ESCC. Combined analysis of E2F1 and cyclin D1 expression helps to determine the characteristics and prognosis of ESCC.     

Inhibitors of histone deacetylases target the Rb-E2F1 pathway for apoptosis induction through activation of proapoptotic protein Bim

Inhibitors of histone deacetylases (HDACIs) are a new generation of anticancer agents that selectively kill tumor cells. However, the molecular basis for their tumor selectivity is not well understood. We investigated the effects of HDACIs on the oncogenic Rb-E2F1 pathway, which is frequently deregulated in human cancers. Here, we report that cancer cells with elevated E2F1 activity, caused either by enforced E2F1 expression, or by E1A oncogene expression, are highly susceptible to HDACI-induced cell death. This E2F1-mediated apoptosis is neither p53- nor p73-dependent but proceeds through selective induction of proapoptotic BH3-only protein Bim. We show that Bim is a direct target of E2F1 and that HDAC inhibition promotes the recruitment of E2F1 to the Bim promoter. Moreover, silencing of Bim by specific small interfering RNA (siRNA) effectively abolishes the E2F1-mediated cell death sensitization to HDACIs. These findings suggest that the oncogenic E2F1 pathway participates in HDACIs-induced apoptosis in cancer cells and underscore the importance of Bim as a key mediator of oncogene-induced apoptosis. Our study provides an important insight into the molecular mechanism of tumor selectivity of HDACIs and predicts that, clinically, HDACIs will be more effective in tumors with high E2F1 activity.     

Sirtuin 1 regulation of developmental genes during differentiation of stem cells

The longevity-promoting NAD⁺–dependent class III histone deacetylase Sirtuin 1 (SIRT1) is involved in stem cell function by controlling cell fate decision and/or by regulating the p53-dependent expression of NANOG. We show that SIRT1 is down-regulated precisely during human embryonic stem cell differentiation at both mRNA and protein levels and that the decrease in Sirt1 mRNA is mediated by a molecular pathway that involves the RNA-binding protein HuR and the arginine methyltransferase coactivator-associated arginine methyltransferase 1 (CARM1). SIRT1 down-regulation leads to reactivation of key developmental genes such as the neuroretinal morphogenesis effectors DLL4, TBX3, and PAX6, which are epigenetically repressed by this histone deacetylase in pluripotent human embryonic stem cells. Our results indicate that SIRT1 is regulated during stem cell differentiation in the context of a yet-unknown epigenetic pathway that controls specific developmental genes in embryonic stem cells.     

汉防己甲素抑制PANC-1细胞增殖作用的机制探讨

目的：探讨汉防己甲素对人胰腺癌细胞株PANC-1细胞增殖的影响及其相关机制。方法：采用MTT法观察汉防己甲素对人胰腺癌细胞株PANC-1细胞增殖的影响;流式细胞术检测其对PANC-1细胞周期及凋亡的影响;实时定量PCR检测细胞周期和凋亡相关基因P21^cip/waf1、cdc25A、c-Myc、E2F1和survivin mRNA水平的变化;Western blot检测P21^cip/waf1蛋白水平的改变。结果：MTT结果显示汉防己甲素对PANC-1细胞增殖抑制作用呈明显的剂量和时间依赖性。经汉防己甲素处理后,流式细胞术检测到明显的G1期细胞阻滞和细胞凋亡。实时定量PCR结果显示,汉防己甲素处理早期,P21^cip/waf1mRNA水平明显增加,而cdc25A、c-Myc、2F1、survivin mRNA水平均下降。Western blot结果表明P21^cip/waf1蛋白水平在汉防己甲素处理早期升高。结论：我们的研究表明汉防己甲素能有效的抑制人胰腺癌细胞株PANC-1细胞增殖。该过程可能通过上调21^cip/waf1mRNA和蛋白的表达,下调cdc25A、c-Myc、E2F1mRNA的表达,致使PANC-1细胞G1期阻滞;也可能通过下调survivin mRNA的表达,诱导PANC-1细胞凋亡。