PcG蛋白在干细胞调控中的作用

PcG (polycomb group)蛋白作为一种表观遗传修饰系统,在动物和植物中具有 保守性.从功能上讲,PcG蛋白可以分为PRC1（polycomb repressive complex 1）和 PRC2（polycomb repressive complex 2）两个核心蛋白复合体. PRC2含有组蛋白甲 基化酶的活性,而PRC1在泛素连接酶E3介导的组蛋白泛素化中发挥作用,二者通过对 组蛋白的修饰控制靶基因转录. 近来研究表明,PcG蛋白对干细胞数量维持和命运转变 有重要的调控作用,其成员表达失调或缺失导致许多恶性肿瘤的发生或导致植物细胞 丧失分化能力、形成愈伤组织. 本文简要综述了PcG蛋白的组成及其在干细胞调控中 的作用.     

Discovery of PPi-type Phosphoenolpyruvate Carboxykinase Genes in Eukaryotes and Bacteria

Phosphoenolpyruvate carboxykinase (PEPCK) is one of the pivotal enzymes that regulates the carbon flow of the central metabolism by fixing CO₂ to phosphoenolpyruvate (PEP) to produce oxaloacetate or vice versa. Whereas ATP- and GTP-type PEPCKs have been well studied, and their protein identities are established, inorganic pyrophosphate (PP_i)-type PEPCK (PP_i-PEPCK) is poorly characterized. Despite extensive enzymological studies, its protein identity and encoding gene remain unknown. In this study, PP_i-PEPCK has been identified for the first time from a eukaryotic human parasite, Entamoeba histolytica, by conventional purification and mass spectrometric identification of the native enzyme, followed by demonstration of its enzymatic activity. A homolog of the amebic PP_i-PEPCK from an anaerobic bacterium Propionibacterium freudenreichii subsp. shermanii also exhibited PP_i-PEPCK activity. The primary structure of PP_i-PEPCK has no similarity to the functional homologs ATP/GTP-PEPCKs and PEP carboxylase, strongly suggesting that PP_i-PEPCK arose independently from the other functional homologues and very likely has unique catalytic sites. PP_i-PEPCK homologs were found in a variety of bacteria and some eukaryotes but not in archaea. The molecular identification of this long forgotten enzyme shows us the diversity and functional redundancy of enzymes involved in the central metabolism and can help us to understand the central metabolism more deeply.     

广西中泥盆世腕足动物空间分布及古环境意义

统计广西中泥盆世不同沉积相区二十条剖面的腕足动物化石记录共计13目45科69属167种,其中Eifelian期47属73种,Givetian期32属100种.对不同级别分类单元的多样性分析表明,从Eifelian期到Givetian期,不仅腕足动物各个目的组成及多样性结构有明显改变,而且各个时期不同沉积环境下的腕足动物...     

高罗王冠虫（Coronocephalus gaoluoensis Wu, 1979）的再研究

标本采自湖南省永顺县万民乡志留系下部Llandovery统Telychian阶秀山组上部,几乎全部为Coronocephalus gaoluoensis Wu,其中有20多块头、胸、尾相连的完整标本。研究发现,Coronocephalus gaoluoensis Wu具有十分特殊的头部构造,其面线前支横切头鞍前叶中前部...     

鞘喙蝽总科（半翅目）在中国的首次发现

半翅目鞘喙亚目是一类具有重要演化意义的昆虫。该亚目包括三个科：鞘喙蝽科(Peloridiidae)和卡拉蝽科(Karabasiidae)同属于鞘喙蝽总科;原臭虫科(Progonocimicidae)属于原臭虫总科。鞘喙蝽科是唯一的现生类群,孑遗于南半球。卡拉蝽科化石较丰富,但只发现于中亚、西伯利亚和蒙古中生代地层。本文...     

硝态氮对黄瓜子叶谷氨酰胺合成酶和谷氨酸脱氢酶活性的影响

在硝态氮存在或缺乏的条件下,测定了黄瓜(Cucumis sativus L．)种子萌发和子叶发育过程中子叶可溶性蛋白质含量以及谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(NAD(H)-GDH)活性的变化。在子叶发育初期,无论外源氮存在与否,每对子叶可溶性蛋白质含量和GS、NADH—GDH、NAD^ -GDH活性随发育上升。在外源氮存在下,第4d后,可溶性蛋白质含量虽有所下降,但基本保持恒定;第6d后,GS和NADH—GDH活性逐渐降低,NAD^ -GDH却相反增高。但在无外源氮条件下,于第4d后,可溶性蛋白质水平以及GS、NADH—GDH和NAD^ -GDH活性都逐渐降低。在子叶发育的整个过程中,外源氮对GS和NAD^ -GDH活性有促进作用,尤其是在子叶发育的后期对NAD^ -GDH活性的促进更为明显。     

串联表达马立克氏病病毒糖蛋白B主要抗原决定簇基因的重组鸡痘病毒的构建

马立克氏病(Marek's disease,MD)是由马立克氏病病毒(Marek's disease virus,MDV)引起的一种具有高度传染性、淋巴组织增生性疾病,病理上以外周神经、性腺、虹膜、各种脏器和皮肤发生单核细胞浸润为特征[1].MD是世界上最重要的家禽传染病之一,是造成世界养禽业重大经济损失的一个主要原因.20世纪70年代早期MD疫苗的发现才使MD得到控制[2].     

人干扰素ω(huIFN-ω)的高效表达、纯化及生物学活性

为了获得人干扰素-ω(huIFN-ω)在大肠杆菌中的高效表达,根据大肠杆菌的偏爱密码子,人工设计并合成了huIFN-ω高表达基因,并克隆到原核表达载体pBV220,在大肠杆菌DH5α中实现了高效表达,目的蛋白占细胞总蛋白的15%左右,以包涵体形式存在.表达产物经变性、复性及阳离子和分子筛层析纯化,纯度达90%以上,产物的抗病毒活性约为1.0×108IU/mg,并具有体外促NK杀伤活性.此结果为进一步研究和开发重组huIFN-ω奠定了基础.     

五株鸽副粘病毒国内分离株F基因片段的克隆与分子特性

鸽Ⅰ型副粘病毒病(鸽瘟)是由鸽Ⅰ型副粘病毒(Pigeon paramyxivirus-Ⅰ,PPMV-Ⅰ)引起的一种高度接触性传染病,是危害养鸽业的主要疫病之一.     

猪瘟病毒C株兔脾毒在SK6细胞中的增殖培养及其鉴定

Enzyme-linked immunosorbent assay(ELISA), direct florescent antibody staining, and RT-PCT were used to detect growth characteristics of Cassical swine fever virus C-strain (Derived from Spleen) in SK6 cell. The results indicated than C-strain (Derived from Spleen) can grow in SK6 cell at a lower level. Direct florescent antibody staining method was not suitable for the detection of attenuated lapinized C-strain. The study provided a primary guide for the detection of attenuated classical swine fever virus. It also supplies an elementary foundation for the study of its growth characteristic in SK6.