Habitat-induced reciprocal transformation in the root phenotype of Oriental ginseng is associated with alteration in DNA methylation

Oriental ginseng is an important medicinal plant that grows in 2 major forms or ecotypes, wild and domesticated. Each form differs conspicuously in root phenotype, but can be converted from one type to another by habitat. Here we show that the habitat-induced transformation of ginseng root phenotype was accompanied by alteration in cytosine methylation at a large number of 5′-CCGG-3′ sites detected by the methylation-sensitive polymorphism (MSAP) marker. The collective CG and CHG methylation levels of all 4 landraces of the domesticated form were significantly lower than those of the wild form. Interestingly, artificially transplanted ginseng plants recreated in both directions the methylation levels (at least in CHG) of their natural counterparts. The methylation differences between the 2 ginseng ecotypes were validated at 2 isolated MSAP loci bearing homology to a 5S rRNA gene or a copia retrotransposon. Our results implicate a link between epigenetic variation and habitat-induced phenotypic flexibility in Oriental ginseng.     

Role of Tip60 tumor suppressor in DNA repair pathway

To prevent the damage caused by DNA strand breaks, eukaryotic cells have evolved a series of highly conserved DNA repair mechanisms. The ubiquitously expressed acetyltransferase, Tip60, plays a central role in ATM (ataxia-telangiectasia mutated) activation which is involved in DNA repair. Recent work uncovered a new mechanism of ATM activation mediated by Tip60 and demonstrated that histone methylation, specifically, trimethylation of histone H3, is a key factor in the process. Here, we review the current understanding of how Tip60 is activated and how it activates ATM in response to DNA damage.     

Histone methylation and ubiquitination with their cross-talk and roles in gene expression and stability

Methylation of lysine residues of histones is associated with functionally distinct regions of chromatin, and, therefore, is an important epigenetic mark. Over the past few years, several enzymes that catalyze this covalent modification on different lysine residues of histones have been discovered. Intriguingly, histone lysine methylation has also been shown to be cross-regulated by histone ubiquitination or the enzymes that catalyze this modification. These covalent modifications and their cross-talks play important roles in regulation of gene expression, heterochromatin formation, genome stability, and cancer. Thus, there has been a very rapid progress within past several years towards elucidating the molecular basis of histone lysine methylation and ubiquitination, and their aberrations in human diseases. Here, we discuss these covalent modifications with their cross-regulation and roles in controlling gene expression and stability. Received 24 September 2008; received after revision 21 November 2008; accepted 28 November 2008     

模板甲基化水平对鼠肝RNA聚合酶体外转录活性的影响

利用３Ｈ－ＵＴＰ同位素参入法，研究了大鼠肝细胞ＲＮＡ聚合酶在核内外的转录活性，结果表明：在细胞核内的转录活性明显低于在无核抽提物中的转录活性。利用自身的ＤＮＡ模板，优于利用外加的ＤＮＡ模板。并比较了不同ＤＮＡ甲基化水平的模板对ＲＮＡ聚合酶体外转录活性的影响，发现模板的甲基化水平与其体外转录水平呈反相关。     

Gene inactivation triggered by recognition between DNA repeats

This chapter focuses on phenomena of gene inactivation resulting from the presence of repeated gene copies within the genome of plants and fungi, and on their possible relationships to homologous DNA-DNA interactions. Emphasis is given to two related premeiotic processes: Methylation Induced Premeiotically (MIP) and Repeat-Induced Point mutation (RIP) which take place in the fungiAscobolus immersus andNeurospora crassa, respectively. The relationships between these processes and genetic recombination are discussed.     

泰必利中间体-2-甲氧基-5-甲磺酰基苯甲酸的新合成法

本文叙述文题化合物(Ⅱ)的合成方法改进。2-甲氧基苯甲酸经氯磺化反应生成2-甲氧基-5-氯磺酰基苯甲酸(Ⅲ),Ⅲ用亚硫酸钠在碳酸氢钠存在下进行还原反应,得2-甲氧基-5-亚磺酸苯甲酸二钠盐(Ⅳ),Ⅳ直接用硫酸二甲酯甲基化、酸析而得产物Ⅱ,收率以Ⅲ计约70%。     

卵巢癌中的表观遗传修饰

介绍了在卵巢癌的发展和治疗中表观遗传学的重要性，特别强调了在卵巢癌中内源性和获得性耐药性遗传途径中异常的DNA甲基化和组蛋白去乙酰化的重要性．通过表观遗传治疗反转肿瘤抑制基因沉寂和其他参与药物级联反应的基因沉寂为出现耐药性的卵巢癌患者带来了新的希望．     

自养小球藻中多糖PCA1的化学结构研究

选取自养小球藻(Chlorella autotrophica)为研究对象,从中分离纯化得到3个组分,对其中的组分PCA1进行研究.电泳及高效凝胶过滤色谱法(HPGFC)鉴定其为均一多糖组分,熔点为226.9℃.相对分子量为1.3×105,气相色谱法及红外光谱显示其主要由α-D-吡喃葡萄糖组成,并含有一定量硫酸基.甲基化及13C-NMR结果表明PCA1是一种以1,4-的α-D-吡喃葡萄糖构成的均一多糖.