组蛋白去乙酰化酶抑制剂诱导肿瘤细胞凋亡的机制

组蛋白去乙酰化酶抑制剂（HDACi）是一类新的化疗药物,能够有效抑制组蛋白去乙酰化酶的活性,促进组蛋白及非组蛋白的乙酰化修饰,在转录和翻译后修饰水平调控肿瘤靶蛋白及凋亡相关蛋白的表达和降解,活化凋亡信号通路,诱导肿瘤细胞凋亡。HDACi抑制抗氧化蛋白的表达,提高细胞内活性氧的水平,引起细胞的氧化损伤。因此,氧化损伤诱导的细胞凋亡也是HDACi杀伤肿瘤细胞的重要机制。HDACi诱导细胞凋亡机制的发现将进一步促进HDACi在临床治疗中的应用。     

组蛋白乙酰化／去乙酰化作用与真核基因转录调控

核小体组蛋白的翻译后修饰是真核基因转录调控中的关键步骤。对于组蛋白的这类修饰方式 ,近年来研究最为活跃的是组蛋白Ｎ末端区域保守的Ｌｙｓ上ε ＮＨ 3 的乙酰化作用。随着各种组蛋白乙酰化酶 /去乙酰化酶被克隆、鉴定 ,组蛋白乙酰化 /去乙酰化作用与真核基因转录调控之间的关系也开始逐步得以阐明。1 .真核转录相关的组蛋白乙酰化酶和组蛋白去乙酰化酶1 .1　组蛋白乙酰化酶 (ｈｉｓｔｏｎｅａｃｅｔｙｌｔｒａｎｓ ｆｅｒａｓｅ ,ＨＡＴ)　　核小体组蛋白中Ｎ末端区域上保守的Ｌｙｓ的乙酰化是染色质具有转录活性的标志之一。在组蛋白…     

组蛋白乙酰化与癌症

由于组蛋白被修饰所引起的染色质结构的改变,在真核生物基因表达调控中发挥着重要的作用,这些修饰主要包括甲基化、乙酰化、磷酸化和泛素化等,其中组蛋白乙酰化尤为重要.组蛋白乙酰转移酶（HAT）和组蛋白去乙酰化酶（HDAC）参与决定组蛋白乙酰化状态.HAT通常作为多亚基辅激活物复合体的一部分,催化组蛋白乙酰化,导致染色质结构的松散、激活转录;而HDAC是多亚基辅抑制物复合体的一部分,使组蛋白去乙酰化,导致染色质集缩,并抑制基因的转录. 编码这些酶的基因染色体易位易于导致急性白血病的发生.另一方面,已经确定了一些乙酰化修饰酶的基因在染色体上的位置,它们尤其倾向定位于染色体的断裂处.综述了HAT和HDAC参与的组蛋白乙酰化与癌症发生之间关系的最新进展,以期进一步阐明组蛋白乙酰化修饰酶的生物学功能以及它们在癌症发生过程中的作用.     

组蛋白去乙酰化酶抑制剂调控干细胞分化与体细胞重编程的研究进展

表观遗传调控,如组蛋白乙酰化修饰,是决定干细胞分化方向的重要机制。组蛋白去乙酰化酶抑制剂(HDACi)通过影响不同亚类的组蛋白去乙酰化酶(HDAC)活性,提高组蛋白乙酰化水平,调控基因表达,从而影响胚胎干细胞自我更新,以及沿神经元、心肌和造血等细胞谱系的定向分化。HDACi类小分子化合物在体细胞重编程中也有广泛的应用,可替代致癌因子c-Myc和Klf4,促进体细胞克隆。研究显示,HDACi的效应与药物剂量、细胞类型和细胞分化状态密切相关。本文主要阐述了HDACi在干细胞分化和体细胞重编程中的应用进展,并对所涉及的分子通路进行讨论,有助于揭示干细胞定向分化的关键分子机制,优化干细胞定向分化诱导策略,对干细胞诱导分化具有重要的理论和实用价值。     

组蛋白去乙酰化酶11的免疫调控功能及其在免疫相关疾病中的作用研究进展

组蛋白乙酰化是一种重要的表观遗传修饰,受到组蛋白乙酰转移酶和组蛋白去乙酰化酶的动态调节。组蛋白去乙酰化酶11 (histone deacetylases 11, HDAC11)是IV类HDAC的唯一成员,能够催化组蛋白和非组蛋白赖氨酸残基去乙酰化并具有去脂酰化活性。HDAC11与免疫细胞的成熟、分化和功能密切相关,多数研究显示HDAC11通过负调控IL-10和上调促炎细胞因子发挥免疫激活作用,但HDAC11也负调控中性粒细胞和T细胞的功能,发挥免疫抑制作用。最近报道HDAC11在炎症反应、肿瘤免疫、移植免疫、自身免疫疾病中发挥重要作用,是免疫治疗的重要靶点。该文就HDAC11的生物学特性、免疫调控功能、在免疫相关性疾病中的作用及其抑制剂开发的最新研究进展作一综述。     

组蛋白去乙酰化酶抑制剂(HDAIs)对异染色质的作用

组蛋白乙酰化和去乙酰化可调节染色体的多种功能,例如基因表达和染色体分离等。研究发现,组蛋白去乙酰化酶抑制剂(histone deacetylase inhibitors,HDACIs)可诱导分化、生长阻断和肿瘤细胞凋亡,目前HDACIs正作为抗肿瘤药物进行临床试验,在肿瘤治疗中显示出具有较好的应用前景。然而,人们对于HDACIs在生物体内是如何发挥作用以及不同类型细胞为何会有不同的应答途径却关注甚少。本综述通过讨论HDACIs对周期和非周期细胞中组蛋白去乙酰化酶的抑制结果,来阐明组蛋白乙酰化模式的动力学特征,特别是对基因组异染色质的作用。     

组蛋白去乙酰化酶4与人类疾病北大核心CSCD

组蛋白去乙酰化酶4(histone deacetylase 4,HDAC4)是一类依赖锌的去乙酰化酶,属于Ⅱ类组蛋白去乙酰化酶(histone deacetylases,HDACs),主要具有去乙酰化酶的活性。HDAC4由去乙酰化酶结构域发挥去乙酰化酶的作用,还具有核定位序列和核输出序列,通过转录后与翻译后水平的修饰可在细胞核和细胞质之间穿梭,进而参与多种调节过程。近年来的研究发现,HDAC4可参与基因的转录调控、细胞凋亡、代谢等诸多生物进程,在多种疾病的发生发展中发挥重要作用。本文主要从HDAC4的结构、去乙酰作用、自身的修饰及其在核浆中的穿梭作用对其进行概述,同时对其在骨关节炎、心血管疾病、肌萎缩性侧索硬化症等不同疾病中的作用、相关的分子机制及组蛋白抑制剂在肿瘤中的应用等方面的研究进展进行综述。     

综述: 组蛋白去乙酰化酶的结构及应用

组蛋白赖氨酸乙酰化是目前研究最为广泛和深入的组蛋白翻译后修饰之一,在染色质重塑和基因表达调控等方面发挥重要作用,这种修饰在体内受到组蛋白乙酰化酶和去乙酰化酶的高度动态调控．除了以组蛋白为底物外,组蛋白去乙酰化酶还可以催化多种非组蛋白的去乙酰化,参与多种生命过程的调节．本文围绕四类人源组蛋白去乙酰化酶,综述了其分类依据、结构与功能特点、催化反应的分子机制,以及针对这些组蛋白去乙酰化酶的抑制剂和激动剂的开发和应用等方面的研究进展．     

组蛋白去乙酰化酶抑制剂作为放射增敏剂抗肿瘤作用机制研究进展

放射治疗是很多类型的恶性实体肿瘤的标准治疗方法之一,但是放射治疗除了存在一些严重的副作用以外很多恶性肿瘤细胞还具有抵抗放射线的功能,这就导致放射线治疗的局限性以及疗效的减弱。组蛋白超乙酰化作用可以使紧缩的核小体变得松弛,调控细胞凋亡及分化相关基因(Bim and Bmf)的表达,诱导细胞凋亡及分化,增强恶性肿瘤细胞对于放射线的敏感性。组蛋白去乙酰化酶抑制剂可以诱导组蛋白超乙酰化,用于恶性肿瘤的治疗,同时组蛋白去乙酰化酶抑制剂作为放射增敏剂有明显的抗肿瘤作用,并减少放射线治疗的剂量级照射时间,明显减轻放射线引起的副作用。组蛋白去乙酰化酶抑制剂很有可能成为肿瘤分子治疗的新靶点。检索近年来的SCI文章,国内外的学者主要是在蛋白质层面阐述组蛋白去乙酰化酶抑制剂作为放射增敏剂抗肿瘤作用机制,本文首次提出组蛋白去乙酰化酶抑制剂增强放射线促进恶性肿瘤细胞凋亡的特定基因(Bim and Bmf)并结合最新的组蛋白去乙酰化酶抑制剂分类进行综述。     

组蛋白去乙酰化酶4与人类疾病

组蛋白去乙酰化酶4（histone deacetylase 4,HDAC4）是一类依赖锌的去乙酰化酶,属于Ⅱ类组蛋白去乙酰化酶（histone deacetylases,HDACs）,主要具有去乙酰化酶的活性。HDAC4由去乙酰化酶结构域发挥去乙酰化酶的作用,还具有核定位序列和核输出序列,通过转录后与翻译后水平的修饰可在细胞核和细胞质之间穿梭,进而参与多种调节过程。近年来的研究发现,HDAC4可参与基因的转录调控、细胞凋亡、代谢等诸多生物进程,在多种疾病的发生发展中发挥重要作用。本文主要从HDAC4的结构、去乙酰作用、自身的修饰及其在核浆中的穿梭作用对其进行概述,同时对其在骨关节炎、心血管疾病、肌萎缩性侧索硬化症等不同疾病中的作用、相关的分子机制及组蛋白抑制剂在肿瘤中的应用等方面的研究进展进行综述。     

Inhibition of histone deacetylase activity is a novel function of the antifolate drug methotrexate

Methotrexate (MTX) is a dihydrofolate reductase (DHFR) inhibitor widely used for treating human cancers, and overexpression of histone deacetylase (HDAC) is usually found in tumors. HDAC inhibitors (HDACi) can reactivate tumor suppressor genes and serve as potential anti-cancer drugs. In this study, we found that MTX shared structural similarity with some HDACi and molecular modeling showed that MTX indeed docks into the active site of HDLP, a bacterial homologue of HDAC. Subsequent in vitro assay demonstrated MTX’s inhibition on HDAC activity in human cancer cells. The global acetylation of histone H3 was also induced by MTX. Moreover, MTX inhibited immunoprecipitated HDAC1/2 activity but not their protein levels. This study provides evidence that MTX inhibits HDAC activity.     

HDAC inhibitor protects chronic cerebral hypoperfusion and oxygen‐glucose deprivation injuries via H3K14 and H4K5 acetylation‐mediated BDNF expression

Vascular dementia (VaD) is the second most common cause of dementia, but the treatment is still lacking. Although many studies have reported that histone deacetylase inhibitors (HDACis) confer protective effects against ischemic and hypoxic injuries, their role in VaD is still uncertain. Previous studies shown, one HDACi protected against cognitive decline in animals with chronic cerebral hypoperfusion (CCH). However, the underlying mechanisms remain elusive. In this study, we tested several 10,11‐dihydro‐5H‐dibenzo[b,f]azepine hydroxamates, which act as HDACis in the CCH model (in vivo), and SH‐SY5Y (neuroblastoma cells) with oxygen‐glucose deprivation (OGD, in vitro). We identified a compound 13, which exhibited the best cell viability under OGD. The compound 13 could increase, in part, the protein levels of brain‐derived neurotrophic factor (BDNF). It increased acetylation status on lysine 14 residue of histone 3 (H3K14) and lysine 5 of histone 4 (H4K5). We further clarified which promoters (I, II, III, IV or IX) could be affected by histone acetylation altered by compound 13. The results of chromatin immunoprecipitation and Q‐PCR analysis indicate that an increase in H3K14 acetylation leads to an increase in the expression of BDNF promoter II, while an increase in H4K5 acetylation results in an increase in the activity of BDNF promoter II and III. Afterwards, these cause an increase in the expression of BDNF exon II, III and coding exon IX. In summary, the HDACi compound 13 may increase BDNF specific isoforms expression to rescue the ischemic and hypoxic injuries through changes of acetylation on histones.     

Methods for the analysis of histone H3 and H4 acetylation in blood

LBH589 is one of the many histone deacetylase inhibitors (HDACi) that are currently in clinical trial. Despite their wide-spread use, there is little literature available describing the typical levels of histone acetylation in untreated peripheral blood, the treatment and storage of samples to retain optimal measurement of histone acetylation nor methods by which histone acetylation analysis may be monitored and measured during the course of a patient’s treatment. In this study, we have used cord or peripheral blood as a source of human leukocytes, performed a comparative analysis of sample processing methods and developed a flow cytometric method suitable for monitoring histone acetylation in isolated lymphocytes and liquid tumors. Western blotting and immunohistochemistry techniques have also been addressed. We have tested these methods on blood samples collected from four patients treated with LBH589 as part of an Australian Children’s Cancer Clinical Trial (CLBH589AAU03T) and show comparable results when comparing in vitro and in vivo data. This paper does not seek to correlate histone acetylation levels in peripheral blood with clinical outcome but describes methods of analysis that will be of interest to clinicians and scientists monitoring the effects of HDACi on histone acetylation in blood samples in clinical trials or in related research studies.     

Copper induces histone hypoacetylation through directly inhibiting histone acetyltransferase activity

The abnormal accumulation of Cu2+ is closely correlated with the incidence of different diseases, such as Alzheimer's disease and Wilson disease. To study in vivo functions of Cu2+ will lead to a better understanding of the nature of these diseases. In the present study, effect of Cu2+ on histone acetylation was investigated in human hepatoma cells. Exposure of cells to Cu2+ resulted in a significant decrease of histone acetylation, as indicated by the decrease of the overall histone acetylation and the decrease of histone H3 and H4 acetylation. Since histone acetyltransferase (HAT) and histone deacetylase (HDAC) are the enzymes controlled the state of histone acetylation in vivo, we tested their contribution to the inhibition of Cu2+ on histone acetylation. One hundred nanomolar trichostatin A, the specific inhibitor of HDAC, did not attenuate the inhibitory effect of Cu2+ on histone acetylation. Combined with that Cu2+ showed no effect on the in vitro activity of HDAC, these results led to the conclusion that it is HAT, but not HDAC that is involved in Cu2+ -induced histone hypoacetylation. This conclusion was confirmed by the facts that (1) Cu2+ significantly inhibited the in vitro activity of HAT, (2) Cu2+ -treated cells possessed a lower HAT activity than control cells, and (3) 50 or 100 microM bathocuproine disulfonate, a chelator of Cu2+, significantly attenuated the inhibition of Cu2+ on HAT activity and histone acetylation in the similar pattern. Combined with that Cu2+ showed no or obvious cytotoxicity at 100 or 200 microM in human hepatoma cells, and the previous study that Cu2+ inhibits the histone H4 acetylation of yeast cells at nontoxic or toxic levels, the data presented here suggest that inhibiting histone acetylation is probably one general in vivo function of Cu2+, where HAT is its molecular target.     

Epigenetic discrimination by mouse metaphase II oocytes mediates asymmetric chromatin remodeling independently of meiotic exit

In mammalian fertilization, paternal chromatin is exhaustively remodeled, yet the maternal contribution to this process is unknown. To address this, we prevented the induction of meiotic exit by spermatozoa and examined sperm chromatin remodeling in metaphase II (mII) oocytes. Methylation of paternal H3-K4 and H3-K9 remained low, unlike maternal H3, although paternal H3-K4 methylation increased in zygotes. Thus, mII cytoplasm can sustain epigenetic asymmetry in a cell-cycle dependent manner. Paternal genomic DNA underwent oocyte-mediated cytosine demethylation and acquired maternally-derived K12-acetylated H4 (AcH4-K12) independently of microtubule assembly and maternal chromatin. AcH4-K12 persisted without typical maturation-associated deacetylation, irrespective of paternal pan-genomic cytosine methylation. Contrastingly, somatic cell nuclei underwent rapid H4 deacetylation; sperm and somatic chromatin exhibited asymmetric AcH4-K12 dynamics simultaneously within the same mII oocyte. Inhibition of somatic histone deacetylation revealed endogenous histone acetyl transferase activity. Oocytes thus specify the histone acetylation status of given nuclei by differentially targeting histone deacetylase and acetyl transferase activities. Asymmetric H4 acetylation during and immediately after fertilization was dispensable for development when both parental chromatin sets were hyperacetylated. These studies delineate non-zygotic chromatin remodeling and suggest a powerful model with which to study de novo genomic reprogramming.     

Methods for the analysis of histone H3 and H4 acetylation in blood

LBH589 is one of the many histone deacetylase inhibitors (HDACi) that are currently in clinical trial. Despite their wide-spread use, there is little literature available describing the typical levels of histone acetylation in untreated peripheral blood, the treatment and storage of samples to retain optimal measurement of histone acetylation nor methods by which histone acetylation analysis may be monitored and measured during the course of a patient’s treatment. In this study, we have used cord or peripheral blood as a source of human leukocytes, performed a comparative analysis of sample processing methods and developed a flow cytometric method suitable for monitoring histone acetylation in isolated lymphocytes and liquid tumors. Western blotting and immunohistochemistry techniques have also been addressed. We have tested these methods on blood samples collected from four patients treated with LBH589 as part of an Australian Children’s Cancer Clinical Trial (CLBH589AAU03T) and show comparable results when comparing in vitro and in vivo data. This paper does not seek to correlate histone acetylation levels in peripheral blood with clinical outcome but describes methods of analysis that will be of interest to clinicians and scientists monitoring the effects of HDACi on histone acetylation in blood samples in clinical trials or in related research studies.