有机盐对基因启动子的σ因子选择性的影响

用σ＾７０或σ＾３８和核心酶（Ｅ）组成的大肠杆菌ＲＮＡ聚合酶全酶（Ｅσ）对四种启动子进行了体外转录,结果表明,ｌａｃＵＶ５,ｒｐＩＪ主要被Ｅσ＾７０识别,ｋａｔＥ主要被Ｅσ＾３８识别,ｆｉｃ在低盐浓度时被Ｅσ＾７０识别,在高浓度盐时被Ｅσ＾３８识别,Ｅσ＾３８转录特异性启动子所需酶量大于Ｅσ＾７０转录特异性启动子的酶量,在含有分别对σ＾７０或σ＾３８亲和性大的混和启动子的体外转录中,启动子之间不存     

有机盐对基因启动子的σ因子选择性的影响

用σ￣（７０）或σ￣（３８）和核心酶（Ｅ）组成的大肠杆菌ＲＮＡ聚合酶全酶（Ｅσ）对四种启动子进行了体外转录。结果表明：ｌａｃＵＶ５,ｒｐｌＪ主要被Ｅσ￣（７０）识别,ｋａｔＥ主要被Ｅσ￣（３８）识别,ｆｉｃ在低盐浓度时被Ｅσ￣（７０）识别,在高浓度盐时被Ｅσ￣（３８）识别;Ｅσ￣（３８）转录特异性启动子所需酶量大于Ｅσ￣（７０）转录特异性启动子的酶量;在含有分别对σ￣（７０）或σ￣（３８）亲和性大的混和启动子的体外转录中,启动子之间不存在干扰和竞争,转录水平与启动子浓度成正相关。     

σ~(38)识别的启动子-35区核酸序列特征研究

依据部分资料假定大肠杆菌ＲＮＡ聚合酶的σ３８亚单位在特异启动子的－３５区识别的保守序列是－ＴＣＴＣＣＣ－,合成用其它碱基分别取代这一区域每一个碱基的引物,以ｏｓｍＹ基因片段为模板,通过ＰＣＲ扩增成－３５区含不同碱基序列的转录模板,用体外重组的由σ３８和核心酶（Ｅ）组成的全酶（Ｅσ３８）对这些启动子进行体外转录．结果显示含－ＴＣＴＣＣＣ－序列的启动子的转录水平既低于原始的ｏｓｍＹ启动子,又低于经ＰＣＲ扩增的其它序列．综合研究结果推测,这一区域的保守序列是－ＴＣＴＣＴＣ－．     

RNA聚合酶σ~S亚基的研究进展

σ~S(RpoS)是大肠杆菌RNA聚合酶的一个亚基.在压力情况下,如高温、酸、渗透冲击、营养缺陷和生长进入稳定期等能够被诱导,并在一定程度上能够取代σ~(70)与核心酶结合形成全酶,从而激活多数σ~S-依赖的基因的转录.对RpoS调控的基因和它们的启动子序列、调控方式以及它自身的调控进行了简单的综述.     

σ~(38)和RMF对有关基因表达调控的研究

将大肠杆菌的rpoS和rmf基因突变型和野生型菌株分别培养在营养丰富的LB培养基和成分有限的EP培养基上。在相同条件下,进入稳定期后的突变型菌株的活细胞数低于野生菌株。采用 Western blot方法测定了不同基因产物在稳定期的变化。σ~(38)对RNA聚合酶核心酶亚单位结构基因 rpoA、rpoB、rpoC以及groEs和tufA基因的表达影响不大,能抑制crp和促进rmf的表达。RMF在营养丰富的条件下对rpoA、rpoD,groEl、rho、tufA和ompA基因的表达有促进作用,而在EP条件下的影响并不明显,对crp和rpoS的表达分别有抑制和促进作用。     

与结瘤基因nodF的启动子相互重叠的启动子起始一个RNA分子的转录(英文)

在根瘤菌中 ,结瘤基因的表达受到转录水平上复杂的调控。通过体外转录、引物延伸等一系列实验在豌豆根瘤菌中发现一个与结瘤基因nodF的启动子相互重叠 ,但转录方向相反的启动子 ,该启动子特异起始一个新的RNA分子———px2 的转录。Northern印迹确定 px2 的长度为 0 .72kb ,并且证明 px2 的转录是依赖于根瘤菌的与E .coliσ70 同源的sigma因子。px2的转录启始位点在体内、体外均相同 ,它坐落在结瘤基因顺式元件的“nodbox”内。进一步发现 px2 的体外转录受到一个参与结瘤基因调控的蛋白———Px的抑制。有结果显示 ,px2 影响结瘤基因的表达     

细菌RNA聚合酶亚单位研究进展

细菌的转录过程是一个由多种分子共同调控的复杂过程,其中RNA聚合酶(RNA polymerase,RNAP)是催化转录合成RNA的重要酶.作为RNAP中一个独立的亚单位,σ因子(sigma factor)在转录起始过程中起着至关重要的作用.最近的研究表明σ因子参与了转录起始的各个过程,包括启动子的定位、启动子的解链、起始RNA合成、脱离启动子等过程.由于其在细菌转录过程中的重要作用,σ因子正在成为抗菌药物研究的新靶点.本文对σ因子的结构、分类、功能以及以它为中心的调控网络的研究进行综述.     

ECF-σ^5因子参与阿维链霉菌中阿维菌素合成和环境胁迫的研究北大核心CSCD

【目的】研究阿维链霉菌中ECF-σ^5子对阿维菌素合成、形态分化和环境胁迫的调控,为揭示阿维菌素生物合成的调控机制和ECF-σ因子的调控网络提供依据。【方法】构建sig5基因缺失、回补和过表达菌株,通过形态观察和摇瓶发酵实验初步确定σ^5形态分化、菌体生长和阿维菌素合成的影响。进一步通过RT-q PCR、EMSA和Ch IP实验寻找确定σ^5靶基因,再通过胁迫实验揭示σ^5能参与的胁迫反应。【结果】对sig5相关突变株的摇瓶发酵和形态观察结果表明,σ^5阿维菌素合成具有抑制作用,但不影响菌体生长和形态分化。sig5基因缺失导致阿维菌素生物合成途径特异性正调控基因ave R和结构基因ave A1的转录水平提高,但σ^5不与ave R和ave A1的启动子区结合。σ^5结合在自身基因及附近基因SAV612、SAV615、SAV618的启动子区,正调控这些基因及所在操纵子的表达。胁迫实验暗示σ^5能参与渗透压引起的胁迫反应。【结论】ECF-σ^5子在转录水平间接负调控阿维菌素的合成。     

σ~(38)和RMF对有关基因表达调控的研究

将大肠杆菌的rpoS和rmf基因突变型和野生型菌株分别培养在营养丰富的LB培养基和成分有限的EP培养基上。在相同条件下,进入稳定期后的突变型菌株的活细胞数低于野生菌株。采用 Western blot方法测定了不同基因产物在稳定期的变化。Σ~(38)对RNA聚合酶核心酶亚单位结构基因 rpoA、rpoB、rpoC以及groEs和tufA基因的表达影响不大,能抑制crp和促进rmf的表达。RMF在营养丰富的条件下对rpoA、rpoD,groEl、rho、tufA和ompA基因的表达有促进作用,而在EP条件下的影响并不明显,对crp和rpoS的表达分别有抑制和促进作用。     

组蛋白与hAMFR基因启动子的结合对体外转录活性的影响

采用从鸡血红细胞中分离纯化的组蛋白,从ＨｅＬａ细胞核中萃取的含有ＲＮＡ聚合酶Ⅱ和多种Ⅱ类基因转录因子的可溶性抽提物,以及从非洲爪蟾卵细胞核中撮以的萃取物热处理物上清用于核小体构建,以含有人自泌移动因子受体基因启动子序列的ＤＮＡ片段为模板进行体外转录实验,结果表明,组蛋白和转录因子在ｈＡＭＦＲ基因启动子序列上的竞争性结合对转录活性具有重要的影响作用,在启动子区域预先构建的核小体能够抑制转录活性;     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.