RUNX3mRNA在原发性肝癌组织中的表达分析

目前,在已知的大多数肿瘤的发生和发展中存在人RUNT相关转录因子3(RUNX3)基因失活,如肝癌、胃癌、肺癌、喉癌、乳腺癌、前列腺癌、子宫内膜癌和子宫颈癌等肿瘤中均发现RUNX3基因5'CpG岛甲基化,这是抑癌基因RUNX3失活的主要机制[1-2].而RUNX3mRNA与原发性肝癌的相关性研究尚少,现通过检测RUNX3mRNA在原发性肝癌及其癌旁组织中的表达,并分析其与临床病理因素的相关性,以探讨RUNX3基因作为一种可能的肝癌抑制基因与肝癌发生和发展的关系及其意义.     

原发性肝癌多基因异常的研究

肿瘤分子生物学和分子遗传学研究表明：肿瘤的发生和演变为多种遗传学事件积累的结果，其中原癌基因激活和抑癌基因失活是肿瘤发生发展的两类重要遗传学改变原发性肝癌是全球最常见的恶性肿瘤之一，其发病机制尚不清楚．但近几年研究发现多种癌基因的异常表达和结构异常与原发性肝癌有关；限制性片段长度多态性（RFry）分析表明人类肝癌染色体IP，4q，sq，回IP，回扣和17P存在较高频率的余合缺失，提示原发性肝癌的发生、发展还需要多个抑癌基因失活的参与．目前国内外对肝癌癌基因和抑癌基因的研究多集中在单基因异常的报道，缺乏对肝癌…     

PcG蛋白EZH2与消化系肿瘤

PcG蛋白在控制胚胎发育、X染色质失活、基因组印迹、干细胞自我更新以及肿瘤的发生、发展中发挥重要作用。EZH2是PcG蛋白的核心成分，在多种消化系肿瘤中表达增高，并与肿瘤的进展和预后差相关。本文就PcG蛋白的结构、功能以及EZH2在消化系肿瘤中的作用及其机制作一综述。     

RUNX3基因与胰腺癌的关系

人类RUNT相关转录因子3(RUNX3)基因是新近发现的一种肿瘤抑制基因,其失活的主要机制是高甲基化和杂合性缺失。RUNX3基因可能是转化生长因子-β(TGF-β)转导通路中的一处重要环节,参与TGF-β上皮细胞生长的负调控作用。在胰腺癌中发现RUNX3基因表达下调,可能是胰腺癌发生过程中的关键性基因。此文对RUNX3基因的结构、功能及其与胰腺癌之间的关系作一综述。     

人乳腺癌上皮细胞miR-217对EZH2表达的调控作用

目的 验证乳腺癌上皮细胞中miR-217是否通过直接作用于homolog2 zeste基因增强子（EZH2）3＇UTR调控EZH2表达.方法 利用RT-PCR技术检测人正常乳腺上皮细胞系HBL-100及乳腺癌上皮细胞系MCF-7、MDA-MB-231细胞株中的miR-217,在低表达miR-217细胞株中转染miR-217模拟物（miR-217 minics）,在高表达miR-217细胞株中转染miR-217抑制剂（miR-217 inhibitor）;Western blot法检测各实验细胞中的EZH2蛋白.用含有miR-217野生型及突变型识别位点的EZH2 3＇UTR载体（UTREZH2-UTR-WT和EZH2-UTR-MUT）质粒分别转染人胚肾细胞293T,检测其相对荧光素酶活性.结果 miR-217在MDA-MB-231细胞中低表达,转染miR-217 minics后,其EZH2蛋白表达下降;miR-217在HBL-100中高表达,转染miR-217 inhibitor后,其EZH2蛋白表达增高.人胚肾细胞293T中EZH2-UTR-WT的相对荧光素酶活性低于EZH2-UTR-MUT,两者相比,P＜0.05.结论 在乳腺癌上皮细胞中,miR-217对EZH2的表达具有调控作用,且miR-217通过直接靶向EZH2 3＇UTR调控EZH2表达.     

中药对肝癌凋亡相关基因的调节

肝细胞肝癌是最常见的人类致死性恶性肿瘤之一，近年来，细胞凋亡在肝癌发病、诊断、治疗中的研究层出不穷。肝癌细胞凋亡是一个多基因参与的复杂调控机制，当促凋亡基因与抑制凋亡基因失去正常调控，控制某一细胞凋亡的基因失活，则该细胞不能通过凋亡清除变异细胞，进而促使细胞某些癌基因活化、表达，形成肿瘤细胞。     

结肠癌组织中lncRNA XIST、miR-32-5p、EZH2的表达变化及临床意义

目的 观察结肠癌组织中长链非编码RNA(lncRNA)X染色体失活特异性转录本基因(XIST)、微小RNA(miR)-32-5p、基因增强子的人类同源基因(EZH2)的表达变化,并探讨其临床意义.方法 采用实时荧光定量PCR检测86例结肠癌组织和癌旁组织中的lncRNA XIST、miR-32-5p、EZH2,分析ln...     

DNA甲基化与RUNX3抑癌基因在肿瘤中的研究进展

人RUNT相关转录因子3(RUNX3)是近年来发现的一个新的抑癌基因,因其低表达或不表达在多种人类肿瘤的发生发展过程中起着重要作用。启动子区过度甲基化是基因失活的重要原因。此文现对RUNX3的甲基化与肿瘤的相关性研究进展予以综述。     

小干扰RNA沉默垂体瘤转化基因1对肝癌细胞增殖和凋亡水平的影响

肝癌是全世界范围的高发恶性肿瘤,在亚洲的发病率、病死率都很高。肝癌的分子学发病机制尚不完全清楚,包括基因结构和功能的缺陷、癌基因的激活、抑癌基因的失活、细胞周期紊乱、染色体的非整倍体出现以及细胞凋亡途径受阻等。垂体瘤转化基因(PTTG)1是细胞周期调节蛋白,能抑制姐妹染色单体分离,导致染色体不稳定,形成非整倍体。在成人大多数正常组织中PTTG1表达较弱,甚至检测不到,而在垂体肿瘤等多种肿瘤细胞中表达明显升高,PTTG1基因可能是一种潜在的抗癌基因治疗靶点[1]。本研究用小干扰RNA (siRNA)降低肝癌细胞株HepG2、SMMC-7721细胞中PTTG1的表达,检测PTTG1表达下调对肝癌细胞增殖及凋亡的影响,探讨PTTG1对肝癌细胞生物学行为的影响以及作为肝癌治疗靶基因的可能性。     

肝细胞恶性转化与肝癌诊断的特异性标志物

肝细胞癌(HCC)是由病毒、化学致癌物等多病因作用,因癌基因或癌相关基因激活、抗癌基因失活或胚胎期某些癌基因重新复活等诸多因素引起肝细胞生长失控而致癌变,其中数百种基因调控和表达与肝癌发生、发展相关.手术切除仍是肝癌治疗的首选方法,早诊断、早治疗是提高肝癌患者生存率的惟一途径.随着多种"组学"如基因组学、蛋白质组学、转录组学等新技术的发展和对肝癌发生机制研究的深入,越来越多的与肝细胞恶性转化相关分子标志物被发现,有望成为肝癌早期特异性诊断的潜在分子标志物.     

H3K27me3在胃癌中的表达及其临床意义

目的:研究H3K27me3在胃癌细胞和组织中的表达,并分析与临床病理因素的关系,探讨H3K27me3在胃癌发生发展中的作用和意义.方法:应用Western blot方法检测胃癌细胞系SGC7901、BGC823、AGS和正常胃黏膜上皮细胞GES-1中H3K27me3的表达;免疫组织化学方法检测61例胃癌组织及20例正常胃黏膜组织中H3K27me3的表达.结果:与正常胃黏膜细胞GES-1相比,H3K27me3在胃癌细胞SGC7901、BGC823、AGS中高表达;H3K27me3在胃癌组织中阳性表达率为80.3%,并与肿瘤大小、浸润深度、淋巴结转移、血管侵犯、临床分期、TNM分期有关(P=0.049,0.030,0.034,0.025,0.003,0.031),而与患者的性别、年龄、病变部位、分化程度、神经侵犯之间无相关性.结论:H3K27me3在胃癌中高表达,并与肿瘤的侵袭转移有关,可能是胃癌患者重要的预后因子.     

Binding of different histone marks differentially regulates the activity and specificity of polycomb repressive complex 2 (PRC2)

The polycomb repressive complex 2 (PRC2) is the major methyltransferase for H3K27 methylation, a modification critical for maintaining repressed gene expression programs throughout development. It has been previously shown that PRC2 maintains histone methylation patterns during DNA replication in part through its ability to bind to H3K27me3. However, the mechanism by which PRC2 recognizes H3K27me3 is unclear. Here we show that the WD40 domain of EED, a PRC2 component, is a methyllysine histone-binding domain. The crystal structures of apo-EED and EED in complex respectively with five different trimethyllysine histone peptides reveal that EED binds these peptides via the top face of its β-propeller architecture. The ammonium group of the trimethyllysine is accommodated by an aromatic cage formed by three aromatic residues, while its aliphatic chain is flanked by a fourth aromatic residue. Our structural data provide an explanation for the preferential recognition of the Ala-Arg-Lys-Ser motif-containing trimethylated H3K27, H3K9, and H1K26 marks by EED over lower methylation states and other histone methyllysine marks. More importantly, we found that binding of different histone marks by EED differentially regulates the activity and specificity of PRC2. Whereas the H3K27me3 mark stimulates the histone methyltransferase activity of PRC2, the H1K26me3 mark inhibits PRC2 methyltransferase activity on the nucleosome. Moreover, H1K26me3 binding switches the specificity of PRC2 from methylating H3K27 to EED. In addition to determining the molecular basis of EED-methyllysine recognition, our work provides the biochemical characterization of how the activity of a histone methyltransferase is oppositely regulated by two histone marks.     

The genomic landscape of histone modifications in human T cells

To understand the molecular basis that supports the dynamic gene expression programs unique to T cells, we investigated the genomic landscape of activating histone modifications, including histone H3 K9/K14 diacetylation (H3K9acK14ac), H3 K4 trimethylation (H3K4me3), and the repressive histone modification H3 K27 trimethylation (H3K27me3) in primary human T cells. We show that H3K9acK14ac and H3K4me3 are associated with active genes required for T cell function and development, whereas H3K27me3 is associated with silent genes that are involved in development in other cell types. Unexpectedly, we find that 3,330 gene promoters are associated with all of these histone modifications. The gene expression levels are correlated with both the absolute and relative levels of the activating H3K4me3 and the repressive H3K27me3 modifications. Our data reveal that rapidly inducible genes are associated with the H3 acetylation and H3K4me3 modifications, suggesting they assume a chromatin structure poised for activation. In addition, we identified a subpopulation of chromatin regions that are associated with high levels of H3K4me3 and H3K27me3 but low levels of H3K9acK14ac. Therefore, these regions have a distinctive chromatin modification pattern and thus may represent a distinct class of chromatin domains.     

Identification of JmjC domain-containing UTX and JMJD3 as histone H3 lysine 27 demethylases

Covalent modifications of histones, such as acetylation and methylation, play important roles in the regulation of gene expression. Histone lysine methylation has been implicated in both gene activation and repression, depending on the specific lysine (K) residue that becomes methylated and the state of methylation (mono-, di-, or trimethylation). Methylation on K4, K9, and K36 of histone H3 has been shown to be reversible and can be removed by site-specific demethylases. However, the enzymes that antagonize methylation on K27 of histone H3 (H3K27), an epigenetic mark important for embryonic stem cell maintenance, Polycomb-mediated gene silencing, and X chromosome inactivation have been elusive. Here we show the JmjC domain-containing protein UTX (ubiquitously transcribed tetratricopeptide repeat, X chromosome), as well as the related JMJD3 (jumonji domain containing 3), specifically removes methyl marks on H3K27 in vitro. Further, the demethylase activity of UTX requires a catalytically active JmjC domain. Finally, overexpression of UTX and JMJD3 leads to reduced di- and trimethylation on H3K27 in cells, suggesting that UTX and JMJD3 may function as H3K27 demethylases in vivo. The identification of UTX and JMJD3 as H3K27-specific demethylases provides direct evidence to indicate that similar to methylation on K4, K9, and K36 of histone H3, methylation on H3K27 is also reversible and can be dynamically regulated by site-specific histone methyltransferases and demethylases.     

Analysis of hormone- and polynucleotide/histone-binding sites of the chicken intestinal 1,25-dihydroxyvitamin D3 receptor by means of proteolysis

Several discrete forms of the 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] receptor from chicken intestinal cytosol were characterized by ultracentrifugation; gel filtration; DNA-, histone-, dye-ligand-binding affinity; and several other chromatographic media. Formation of altered receptor complexes was carried out through partial proteolysis using trypsin, alpha-chymotrypsin, and papain. The holoreceptor complex was found to be asymmetric and have a Stoke's radius of 37 A. Depending on the concentration of protease, several sterol-binding fragments of 33 and 27 A were produced which tended to be more globular in shape. The 27 A complex was incapable of binding DNA, histones, or phosphocellulose, but still retained affinity for DEAE-cellulose. Resolution of three forms of 1,25-(OH)2D3 receptors was demonstrated by cibacron blue F3GA-agarose chromatography. The 37 A complex eluted at 1.1 M KCl, and the 33 A form eluted at 0.6 M KCl, whereas the 27 A complex was not retained by the column and eluted in the 0.15 M KCl wash. The specificity of the 37 A complex for histone binding was assessed. The order of binding preference was: histone f3 greater than histone f2a approximately equal to histone f2b much greater than histone f1. Results also indicated that DNA could inhibit receptor binding to histone and that this was competitive with respect to histone-agarose binding, suggesting that the interaction of histones and DNA is at a domain common to polynucleotides. It is concluded the 1,25-(OH)2D3 receptor has separate and distinct binding sites for hormone and polynucleotides/histones. These in vitro findings of histone binding suggest that the polynucleotide domain of this receptor is capable of recognizing several nuclear derived components that may be important for the alteration of gene expression.