Nuclear organization of centromeric domains is not perturbed by inhibition of histone deacetylases

It is well established that modification of lysines in histone molecules correlates with gene expression and chromatin structure. It is not known whether this operates entirely at a local level, e.g. through the recruitment of specific proteins, or whether histone modifications might impact on more long-range aspects of chromatin organization. There is a distinctive organization of chromatin within the nucleus and the chromatin at the nuclear periphery of mammalian cells appears to be hypoacetylated. Previously it had been suggested that inhibition of histone deacetylases by TSA causes a gross remodeling of nuclear structure, specifically the recruitment of centromeric heterochromatin to the nuclear periphery. Here, we have quantified the nuclear organization of histone modifications and the localization of centromeric domains in human cells before and after TSA treatment. TSA alters the nuclear distribution of histone acetylation, but not that of histone methylation. TSA elevates levels of histone acetylation at the nuclear periphery but we see no alteration in the position of centromeric domains in the nuclei of treated cells. We conclude that the distinctive nuclear localization of centromeric domains is independent of histone acetylation.     

Histone deacetylase activity is necessary for chromosome condensation during meiotic maturation in Xenopus laevis

Chromosome condensation is thought to be an essential step for the faithful transmission of genetic information during cellular division or gamete formation. The folding of DNA into metaphase chromosomes and its partition during the cell cycle remains a fundamental cellular process that, at the molecular level, is poorly understood. Particularly, the role of histone deacetylase (HDAC) activities in establishing and maintaining meiotic metaphase chromosome condensation has been little documented. In order to better understand how metaphase chromosome condensation is achieved during meiosis, we explored, in vivo, the consequences of HDAC activities inhibition in a Xenopus oocyte model. Our results show that deacetylase activity plays a crucial role in chromosome condensation. This activity is necessary for correct chromosome condensation since the earlier stages of meiosis, but dispensable for meiosis progression, meiosis exit and mitosis entry. We show that HDAC activity correlates with chromosome condensation, being higher when chromosomes are fully condensed and lower during interphase, when chromosomes are decondensed. In addition, we show that, unlike histone H4, Xenopus maternal histone H3 is stored in the oocyte as a hypoacetylated form and is rapidly acetylated when the oocyte exits meiosis.     

曲古抑菌素A对前列腺癌LNCaP细胞雄激素受体的清除作用

目的:研究组蛋白去乙酰化酶抑制剂曲古抑菌素A(trichostatinA,TSA)对前列腺癌细胞的抑制作用机理。方法:四甲基偶唑氮蓝(MTT)检测药物对肿瘤细胞增殖的影响;Hochest33342染色观察细胞凋亡的形态学变化;Western印迹分析雄激素受体(AR)蛋白的表达;反转录PCR检测AR转录水平的变化。结果:TSA在较低浓度即能有效抑制LNCaP细胞的增殖,EC50为125.9nmol·L-1,并诱导肿瘤细胞凋亡;药物处理后细胞周期依赖性蛋白激酶抑制剂p21表达增高,AR呈时间及剂量依赖性被清除。TSA对AR的清除是发生在蛋白水平的降解,而不影响其转录。结论:TSA能够清除对细胞生长具有重要作用的AR细胞信号通路,从而对前列腺癌LNCaP细胞发挥抑制作用。     

Natural indoles,indole-3-carbinol and 3,3′-diindolymethane,inhibit T cell activation by staphylococcal enterotoxin B through epigenetic regulation involving HDAC expression

Staphylococcal enterotoxin B (SEB) is a potent exotoxin produced by the Staphylococcus aureus. This toxin is classified as a superantigen because of its ability to directly bind with MHC-II class molecules followed by activation of a large proportion of T cells bearing specific Vβ-T cell receptors. Commonly associated with classic food poisoning, SEB has also been shown to induce toxic shock syndrome, and is also considered to be a potential biological warfare agent because it is easily aerosolized. In the present study, we assessed the ability of indole-3-carbinol (I3C) and one of its byproducts, 3,3′-diindolylmethane (DIM), found in cruciferous vegetables, to counteract the effects of SEB-induced activation of T cells in mice. Both I3C and DIM were found to decrease the activation, proliferation, and cytokine production by SEB-activated Vβ8 ⁺ T cells in vitro and in vivo. Interestingly, inhibitors of histone deacetylase class I (HDAC-I), but not class II (HDAC-II), showed significant decrease in SEB-induced T cell activation and cytokine production, thereby suggesting that epigenetic modulation plays a critical role in the regulation of SEB-induced inflammation. In addition, I3C and DIM caused a decrease in HDAC-I but not HDAC-II in SEB-activated T cells, thereby suggesting that I3C and DIM may inhibit SEB-mediated T cell activation by acting as HDAC-I inhibitors. These studies not only suggest for the first time that plant-derived indoles are potent suppressors of SEB-induced T cell activation and cytokine storm but also that they may mediate these effects by acting as HDAC inhibitors.     

低氧诱导下舌鳞癌SCC-6细胞中HIF-1α、VEGF的表达及TSA对其表达的抑制

目的:观察低氧与人舌鳞状细胞癌SCC-6细胞中HIF-1α、VEGF表达的相关性,曲古抑菌素A(TSA)对其表达的抑制作用,初步探讨其作用机制。方法:体外培养的舌鳞状细胞癌SCC-6细胞,经不同作用时间去铁胺处理,模拟低氧条件培养后,RT-PCR检测HIF-1α、VEGF的mRNA表达,Western Blot检测其蛋白表达;模拟低氧条件下,不同浓度、时间梯度TSA处理SCC-6细胞后,分别检测HIF-1α、VEGF的mRNA及蛋白表达。结果:①低氧下SCC-6细胞HIF-1α蛋白表达增加,但其mRNA的表达不受影响;作为HIF-1α下游基因的VEGF的mRNA和蛋白表达,随HIF-1α蛋白表达增加而增加;②低氧下,TSA可抑制HIF-1α的蛋白表达及VEGF的mRNA和蛋白表达,并呈量效和时效关系,但HIF-1α的mRNA表达不受影响;③HIF-1α的调节在蛋白水平。结论:体外条件下,模拟低氧可诱导舌鳞状细胞癌SCC-6细胞中HIF-1α蛋白、其下游基因VEGF的mRNA和蛋白的表达增加。TSA可抑制HIF-1α的蛋白表达,进而抑制其下游基因VEGF的表达,从而发挥抗肿瘤血管生成的作用,并且呈量效和时效关系。     

曲古抑菌素A对甲状腺鳞癌SW579细胞株p53和p21表达的影响

目的观察曲古抑菌素A(TSA)对甲状腺鳞癌SW579细胞株生长增殖及p53和p21表达的影响,进而探讨TSA抗甲状腺癌的作用机制。方法体外培养SW579细胞,实验分为DMSO组、TSA组(终浓度为50、100、200、400 nmol/L),采用MTT比色法测定细胞增殖活性;用RT-PCR方法检测SW579细胞p53及p21的mRNA表达;用Western blot方法检测SW579细胞p53及p21的蛋白表达。结果 MTT结果显示,TSA可明显抑制SW579的增殖,并呈剂量依赖性。RT-PCR与Western blot检测结果表明,与未加TSA组比较,TSA组随着浓度的逐渐加大,p21 mRNA和蛋白表达水平明显升高;p53 mRNA表达不变,而p53蛋白表达水平上调。结论 TSA在一定浓度范围内对甲状腺鳞癌细胞株SW579有剂量依赖性地增殖抑制作用,其机制可能与TSA提高SW579细胞p53的表达,进而再上调p21的表达有关。     

曲古霉素A体外诱导膀胱癌细胞凋亡及细胞周期阻滞的机制探讨

目的:观察组蛋白去乙酰化酶(HDAC)抑制剂曲古霉素A(TSA)对体外培养膀胱癌细胞生长情况及相关基因表达的影响,并探讨其可能的作用机制.方法:MTT法检测不同浓度(0.05、0.1、0.2、0.4、0.8 μmol/L)的TSA对人膀胱癌T24细胞生长的影响.透射电镜观察TSA(0.4 μmol/L) 诱导后膀胱癌细胞的形态学变化;流式细胞术检测处理后膀胱癌细胞周期分布及凋亡率的变化;Western 印迹法检测处理后膀胱癌细胞组蛋白乙酰化水平的变化;FQ-PCR检测处理后膀胱癌细胞p21CIP1/WAF1、cyclin A和cyclin E mRNA的表达.结果:TSA体外能明显抑制T24细胞生长,且抑制作用呈明显的剂量、时间依赖性.TSA(0.4 μmol/L)诱导后,透射电镜下可见大量具有凋亡形态特征的T24细胞;流式细胞术检测示细胞阻滞于G0/G1期,并且出现典型的亚二倍体(Sub-G1)峰;TSA可明显提高组蛋白乙酰化水平,并诱导p21CIP1/WAF1的mRNA表达和抑制cyclin A的mRNA表达,而对cyclin E无明显作用.结论:TSA可通过诱导细胞凋亡及细胞周期阻滞而发挥体外抗膀胱癌作用,其作用机制可能涉及组蛋白乙酰化水平以及相关基因(p21CIP1/WAF1、cyclin A)表达的调控.     

曲古菌素A对HL-60细胞组蛋白乙酰化水平和凋亡的作用

本研究旨在探讨曲古菌素A(trichostatinA ,TSA)高效低毒的抗癌机理。应用细胞培养、MTT法 ,免疫细胞化学技术和Annexin V FITC PI双标流式细胞术观察TSA对HL 6 0细胞和正常人外周血单个核细胞 (normalhumanperipheralbloodmononuclearcell,NPBMNC)的生长抑制 ,组蛋白乙酰化水平以及诱导凋亡的影响。结果表明 :TSA能够以时间、剂量依赖性方式抑制HL 6 0细胞增殖 ,36小时IC50 为 10 0ng ml。TSA能够诱导HL 6 0细胞凋亡 ,其作用也呈时间、剂量依赖性。TSA在显著诱导HL 6 0细胞凋亡的浓度和时间范围内对NPBMNC无明显的诱导凋亡作用。TSA处理 4小时后 ,HL 6 0细胞和NPBMNC组蛋白乙酰化水平上调显著高于未用TSA各组 (P<0 .0 5 ) ,但两者之间无显著性差异 (P >0 .0 5 )。结论 :TSA对HL 6 0细胞有明确的抑制增殖能力 ;TSA有明确的诱导HL 6 0细胞凋亡的能力 ,这可能是TSA体外抑制白血病细胞系HL 6 0生长和发挥抗白血病作用的主要机理之一 ;与NPBMNC相比较 ,TSA能够选择性诱导HL 6 0细胞凋亡 ;TSA选择性抑制HL 6 0细胞的机理与TSA调控HL 6 0细胞和NPBMNC组蛋白乙酰化水平的差异无关。     

ＴＳＡ诱导ＭＣＦ-７细胞毒性过程中转录调节的实验研究

目的:研究制滴菌素(trichostatin A,TSA)诱导乳腺癌细胞株MCF-7的细胞毒性作用及基于该效应可能的转录调节基础.方法:采用MTT法观察不同浓度TSA对MCF-7细胞的抑制作用,Annexin-V/PI双染观察该梯度下的细胞凋亡情况,细胞周期分析检测不同时间段的周期变化,RT-PCR分析TSA处理前后ERaα、myc-c、P21、cyclin-D及Bcl-2基因的转录表达情况.结果:TSA对MCF-7细胞的抑制作用具有时间和剂量的依赖性,Annexin-V/PI双染分析显示在TSA处理48 h后,随其浓度的增加,细胞的凋亡率依次升高,0.5 μmol/L TSA作用,细胞凋亡率为33.82%;细胞周期分析检测显示在0.5 μmol/L TSA的作用下,MCF-7细胞出现周期阻滞.但未检测出细胞凋亡.RT-PCR分析显示除P21基因上调外,ERα、myc-c、cyclin-D及Bcl-2均下调,同朝着增殖抑制、周期阻滞及凋亡的方向进展.结论:TSA能诱导MCF-7细胞的细胞毒性作用,其机制可能与转录调节有关.