过表达E2F6基因抑制BRD7基因启动子活性

BRD7基因是采用cDNA代表性差异分析法克隆的一个新Bromodomain基因(GenBank 登录号AF152604)。它在鼻咽癌细胞和组织中表达明显下调,过表达BRD7基因可抑制鼻咽癌细胞的生长和细胞周期的进程。前期工作已克隆了BRD7基因启动子区,并将其启动子定位于450bp（-404→+46bp）的区域。为了进一步揭示BRD7基因在鼻咽癌细胞和组织中表达下调的分子机制,生物信息学分析表明BRD7启动子区有E2F6转录因子结合位点,电泳迁移率实验结果表明转录因子E2F6特异性地结合于BRD7启动子区。荧光素酶检测和绿色荧光蛋白表达检测都证实过表达E2F6基因能抑制BRD7基因启动子活性     

肝细胞癌中转录因子E2F7对Wnt/β-catenin信号通路活性的影响

探讨肝细胞癌(HCC)中非典型性E2F家族成员E2F7在肝癌细胞生长、分化中的作用及可能涉及的分子机制.本研究运用实时荧光定量PCR检测38例原发性肝细胞癌及对应的癌旁组织中E2F7基因mRNA的表达情况;分别通过基因过表达和RNA干扰技术上调或下调E2F7基因表达,并运用实时荧光定量PCR和Western印迹检测肝癌细胞株MHCC-H中β-catenin及其靶基因cmyc的表达情况;双荧光素酶报告基因系统检测E2F7对Wnt/β-catenin信号通路活性的影响;核浆分离实验检测过表达E2F7基因对β-catenin入核的影响;免疫共沉淀实验检测异位表达E2F7与内源β-catenin的相互作用.结果显示,肝细胞癌组织中E2F7基因的表达量显著高于相应的癌旁组织(P0.001);转录因子E2F7可与β-catenin相互作用并促进β-catenin进入细胞核.转录因子E2F7可以促进Wnt/β-catenin信号通路的活性.     

转录因子E2F在细胞周期调控中的重要作用

转录因子E2F在细胞周期调控中起重要作用。E2F的活性受到pRb,细胞周期素和细胞周期素依赖性激酶的控制。近年来,许多有关E2F研究的新进展揭示了E2F与肿瘤发生、细胞凋亡、肿瘤抑制等均有密切关系。     

肿瘤抑制基因Rb与细胞周期调控研究新进展

Rb与人类多种肿瘤发生关系密切,是一种重要的肿瘤抑制基因.Rb蛋白参与细胞周期调控,与p16、CDK4/6、cyclinD1等形成复杂的反馈调节网络,在G1/S关卡调控中处于中心环节,决定着细胞周期的进程.Rb又是核内信号与胞外信号相互作用的界面,受到胞内外多种因素的调控,使Rb功能与细胞生长、分化状态相适应.     

BRD7基因调控区的克隆与功能研究

BRD7基因是采用cDNA代表性差异分析法克隆得到的一个新的Bromodomain基因(GenBank登录号AF152604).它在鼻咽癌细胞和组织中表达明显下调,过表达BRD7基因能部分逆转鼻咽癌细胞的恶性表型.为了揭示BRD7基因在鼻咽癌细胞和组织中表达下调的分子机制,利用生物信息学技术已预测出其启动子区.荧光素酶活性检测结果表明该区域具有强启动子活性;转录因子Sp1特异性地结合于BRD7该启动子区;Sp1特异性阻断剂mithramycinA能明显地抑制BRD7启动子的活性和BRD7基因的表达.     

E2F是疾病治疗的潜在靶点

竞争性寡聚脱氧核糖核酸识别转录因子的DNA结合域,抑制了转录因子对基因的转录调控,转录因子E2F作为潜在的治疗靶点,可以用于抑制肾小球系膜细胞和血管内皮细胞的增生,在部分异常增生的疾病中显示了一定的应用前景。     

RB-E2F信号通路与乳腺癌及其治疗

视网膜母细胞瘤基因（retinoblastoma gene, RB1）突变或调节CDK-RB-E2F通路其他成分的突变存在于几乎所有人类恶性肿瘤中。因此,通过抑制细胞周期蛋白激酶（CDK）来实现对细胞周期的调控,在肿瘤治疗中越来越显示出其优势。目前,CDK4/6抑制剂帕博西尼（palbociclib）联合芳香酶抑制剂,治疗ER 阳性乳腺癌是很有效的临床应用。研究显示,CDK-RB-E2F信号通路,对控制乳腺细胞增殖发挥关键作用。近期的研究结果,揭示了该通路在肿瘤发展、血管生成及转移中的作用。并且,E2Fs是不依赖于其他临床参数的乳腺癌预后指标。本综述总结了乳腺癌中RB E2F通路的最新研究进展,并且讨论应用高通量基因组学研究,筛选获得乳腺癌中CDK4/6抑制剂重要的作用靶点,旨在发展更有效的联合治疗手段。     

转录因子E2F1蛋白纯化及甲基化鉴定

目的:构建人E2F1基因原核表达质粒p GEX-KG-E2F1,并在大肠杆菌中诱导表达。随后验证纯化得到的E2F1蛋白可作为底物被甲基化转移酶修饰。方法:构建原核表达质粒p GEX-KG-E2F1,在大肠杆菌BL-21中经异丙基硫代半乳糖苷(IPTG)诱导表达,利用GST亲和层析法纯化表达的E2F1蛋白。随后将纯化的E2F1蛋白作为底物,组蛋白甲基化转移酶SET7/9作为酶进行体外同位素标记放射自显影实验,检测纯化的E2F1蛋白能否被甲基化。结果:酶切鉴定和测序结果证明成功构建了原核表达载体p GEX-KG-E2F1,SDS-PAGE检测结果证明实现了人E2F1基因在大肠杆菌中的可溶性表达,放射自显影证明纯化得到的E2F1蛋白可作为底物被甲基化转移酶SET7/9甲基化。结论:成功构建了转录因子E2F1体外甲基化体系,为筛选新的能甲基化E2F1的酶奠定基础。     

Wnt/β-catenin信号通路对靶基因转录的调控

Wnt/β-catenin信号通路又被称为经典Wnt信号通路,在早期胚胎发育、成体组织稳态维持、干细胞干性调控和肿瘤发生等过程中均发挥重要作用.经典Wnt信号通路的核心信号转导因子β-catenin与核内转录因子TCF/LEF家族成员结合后,通过募集或替换一系列协同作用因子,诱导染色质结构变化,调控Wnt信号靶基因的转录.本文将从Wnt信号靶基因转录调控的基本模式、分子机制、表观遗传学调控和意义等方面,总结近年来有关Wnt信号靶基因转录调控的研究成果,方便读者更好地理解Wnt信号通路靶基因的转录调控.     

Genomic Deregulation of the E2F/Rb Pathway Leads to Activation of the Oncogene EZH2 in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is a highly aggressive lung neoplasm with extremely poor clinical outcomes and no approved targeted treatments. To elucidate the mechanisms responsible for driving the SCLC phenotype in hopes of revealing novel therapeutic targets, we studied copy number and methylation profiles of SCLC. We found disruption of the E2F/Rb pathway was a prominent feature deregulated in 96% of the SCLC samples investigated and was strongly associated with increased expression of EZH2, an oncogene and core member of the polycomb repressive complex 2 (PRC2). Through its catalytic role in the PRC2 complex, EZH2 normally functions to epigenetically silence genes during development, however, it aberrantly silences genes in human cancers. We provide evidence to support that EZH2 is functionally active in SCLC tumours, exerts pro-tumourigenic functions in vitro, and is associated with aberrant methylation profiles of PRC2 target genes indicative of a “stem-cell like” hypermethylator profile in SCLC tumours. Furthermore, lentiviral-mediated knockdown of EZH2 demonstrated a significant reduction in the growth of SCLC cell lines, suggesting EZH2 has a key role in driving SCLC biology. In conclusion, our data confirm the role of EZH2 as a critical oncogene in SCLC, and lend support to the prioritization of EZH2 as a potential therapeutic target in clinical disease.     

E2F7 and E2F8 keep the E2F family in balance

An article by Li and colleagues (in this issue of Developmental Cell) shows that the atypical E2Fs, E2F7 and E2F8, are critical for mouse development. One of the important functions of these family members stems from a negative feedback loop in which E2F7 and E2F8 limit the expression of E2F1 and prevent E2F1-dependent apoptosis.     

An Intronic microRNA Links Rb/E2F and EGFR Signaling

The importance of microRNAs in the regulation of various aspects of biology and disease is well recognized. However, what remains largely unappreciated is that a significant number of miRNAs are embedded within and are often co-expressed with protein-coding host genes. Such a configuration raises the possibility of a functional interaction between a miRNA and the gene it resides in. This is exemplified by the Drosophila melanogaster dE2f1 gene that harbors two miRNAs, mir-11 and mir-998, within its last intron. miR-11 was demonstrated to limit the proapoptotic function of dE2F1 by repressing cell death genes that are directly regulated by dE2F1, however the biological role of miR-998 was unknown. Here we show that one of the functions of miR-998 is to suppress dE2F1-dependent cell death specifically in rbf mutants by elevating EGFR signaling. Mechanistically, miR-998 operates by repressing dCbl, a negative regulator of EGFR signaling. Significantly, dCbl is a critical target of miR-998 since dCbl phenocopies the effects of miR-998 on dE2f1-dependent apoptosis in rbf mutants. Importantly, this regulation is conserved, as the miR-998 seed family member miR-29 repressed c-Cbl, and enhanced MAPK activity and wound healing in mammalian cells. Therefore, the two intronic miRNAs embedded in the dE2f1 gene limit the apoptotic function of dE2f1, but operate in different contexts and act through distinct mechanisms. These results also illustrate that examining an intronic miRNA in the context of its host''s function can be valuable in elucidating the biological function of the miRNA, and provide new information about the regulation of the host gene itself.     

The Rb/E2F pathway and Ras activation regulate RecQ helicase gene expression

Disruption of the Rb (retinoblastoma protein)/E2F cell-cycle pathway and Ras activation are two of the most frequent events in cancer, and both of these mutations place oncogenic stress on cells to increase DNA replication. In the present study, we demonstrate that these mutations have an additive effect on induction of members of the RecQ DNA helicase family. RecQ activity is important for genomic stability, initiation of DNA replication and telomere maintenance, and mutation of the BLM (Bloom's syndrome gene), WRN (Werner's syndrome gene) or RECQL4 (Rothmund-Thomson syndrome gene) family members leads to premature aging syndromes characterized by genetic instability and telomere loss. RecQ family members are frequently overexpressed in cancers, and overexpression of BLM has been shown to cause telomere elongation. Concomitant with induction of RecQ genes in response to Rb family mutation and Ras activation, we show an increase in the number of telomeric repeats. We suggest that this induction of RecQ genes in response to common oncogenic mutations may explain the up-regulation of the genes seen in cancers, and it may provide a means for transformed cells to respond to an increased demand for DNA replication.