臭鼩高重复顺序DNA的核苷酸顺序分析及其与树鼩TSr(Bgl Ⅱ)-1顺序的比较

将臭鼩DAN经过Bam H Ⅰ酶切得到的高重复顺序DNA最小片段重组到质粒pAT153上,转化后得到了含有臭鼩BMS(Bam H Ⅰ)-1高重复顺序DNA片段的克隆。再把此片段重组到M_(13)mp19噬菌体DNA上。用末端终止法测得全部苷酸顺序为495个碱基对。对臭鼬BMS(Bam H Ⅰ)-1片段的结构特点进行了分析,并和树鼩TSr(BglⅡ)-1高重复顺序DNA进行了比较。为确定树鼩在分类学上的地位,提供了一定的分子遗传学证据。     

恒河猴高重复顺序DNA的分子克隆

哺乳动物基因组中高重复顺序可用限制性内切酶消化DNA经用电泳分离获得,本文用限制性内切酶Bam HI消化恒河猴DNA分离得到一系列高重复片段。用其中最小片段与质粒pBR 322共价连接,转化到大肠杆菌后得到3个带有重组子的克隆。其中PMBI克隆用Bam HI,Pst I酶解,杂交鉴定,证明此克隆是含有重组的恒河猴高重复片段,此片段大小约为340碱基对。哺乳动物基因组相当繁杂,一般在10~9碱基对(b.p)以上,应用复性动力学方法可将其分成高重复顺序、中重复顺序及单拷贝顺序。高重复顺序在基因组中重复频率很高。可达百万次。它有许多家族,这些家族核苷酸顺序相近,但不相同,目前有证据表明,高重复顺序与基因表达及调控有关,与生物进化有关,而且还与DNA的复制及调控有关,因此具有重要的生理功用。为了得到纯的单一高重复顺序,我们应用分子克隆技术,建立了恒河猴高重复顺序DNA的分子克隆。     

懒猴高重复顺序DNA的核苷酸顺序分析及其与类α-DNA顺序的比较

为确知懒猴高重复顺序与灵长类类α顺序间的相互关系,我们将懒猴DNA经EcoRI酶切所得到的高重复顺序DNA的最小片段重组到质粒pUC~(12)上,经转化、筛选、鉴定得到含有懒猴高重复顺序片段的克隆,命名为pLS(EcoR Ⅰ)-1,测定其全部核苷酸顺序为641bp,发现该顺序有与类α顺序的相似性,但变异性较大,我们对此进行了讨论。     

大鼠高重复顺序DNA的核苷酸顺序分析及其与灵长类类α-DNA顺序的比较

 啮齿目动物高重复顺序DNA的结构特征,虽已有人进行过分析,并提出大鼠DNA中有酶切位点分布独特的高重复顺序,也有人认为在Sprague-Dawlay大鼠中有类似于α-DNA大小的高重复顺序,并命名为α型(α-type),是否大鼠中也含有类α顺序,并没有人讨论过。我们对Wistar大鼠高重复顺序DNA进行了分离、纯化、分子克隆及核苷酸序列分析,测定了全序列为370bp,它也是具有酶切点分布独特的高重复顺序,但与前者存在着18％的差异性。我们对此顺序与灵长类类α-DNA进行了比较分析,发现二者在几方面都不存在相似之处,如此序列G-C含量占全部碱基组成的37.3％,而类α顺序的G-C含量约在40％以上,一些酶切位点也与类α-DNA完全不相同,另外在此序列的相应位置上也不具有灵长类类α-DNA的三个“冷点区”等等,由此得出大鼠这一高重复顺序并非类α顺序,而类α顺序只是灵长类动物所特有的。     

树鼩高重复顺序TSr(Bgl-Ⅱ)-1的核苷酸顺序分析及与灵长类α-顺序的比较

为了确知树鼩高重复顺序与灵长类动物的类α顺序有无相似处,我们再次把TSr(BglⅡ)-1片段克隆在质粒pWR33上,用“双链引物测序法”测得全部核苷酸顺序为353bp。并将此顺序与灵长类动物的类α顺序进行比较,发现其中有三个对应位置上与类α顺序的“冷点”保守区序列相似,其中还有一个有碱基变异的EcoRⅠ酶切点和四个潜在的HindⅢ酶切点,另外有两个与“凉点”区一致的小顺序,对这些相似性进行了讨论。     

人类DNA高重复顺序复性产物某些特性的研究

本文对正常人淋巴细胞DNA的高重复顺序某些特性进行了研究。应用复性动力学方法分离了重复顺序并观察了复性后的稳定性。复性后的高重复顺序极易交织成网状结构,用低离子强度缓冲液透析,特别是除去磷酸根离子能使网状结构拆开,而镁离子对这种网状结构有稳定作用。用~(125)Ⅰ标记的高重复顺序用核酸酶S_1处理后热稳定性增加,但T_m值仍低于天然DNA,表明复性后的高重复顺序除包含有单链片段外,碱基对中仍有错配。     

人类DNA高重复顺序复性产物某些特性的研究

本文对正常人淋巴细胞DNA的高重复顺序某些特性进行了研究。应用复性动力学方法分离了重复顺序并观察了复性后的稳定性。复性后的高重复顺序极易交织成网状结构,用低离子强度缓冲液透析,特别是除去磷酸根离子能使网状结构拆开,而镁离子对这种网状结构有稳定作用。用~(125)Ⅰ标记的高重复顺序用核酸酶S_1处理后热稳定性增加,但T_m 值仍低于天然DNA,表明复性后的高重复顺序除包含有单链片段外,碱基对中仍有错配。     

重复顺序与基因表达

一、真核基因组与重复顺序 重复顺序DNA在真核生物基因组中普遍存在,最早研究是在随体中出现。1968年Britten等采用了复性动力学的研究方法获得了可靠的实验证据,并提出了真核基因组中都有高重复顺序,中重复顺序与单考贝DNA顺序。     

一种能表现水稻基因组DNA分化特征的重复DNA顺序

用ＤＮＡ 复性动力学方法克隆到一个水稻中度重复顺序。Ｓｏｕｔｈｅｒｎ 杂交、限制性内切酶分析及序列分析资料表明,该重复顺序在水稻基因组中具有串联重复和散布状态两种存在方式。以该ＤＮＡ 片段作探针,用Ｓｏｕｔｈｅｒｎ 杂交方法分析了多种野生稻种和栽培稻品种的基因组分化特征。某些限制性内切酶消化过的水稻ＤＮＡ,其图谱呈现出多达４０ 条以上的杂交带,包括强杂交带和弱杂交带两种类型。重复实验结果证明,强杂交带表现为ＢＢＣＣ染色体组型特异而弱带则在栽培稻各品种间显示出丰富的多态性,表明该重复顺序片段在水稻理论研究和育种实践中可能具有重要意义     

真核细胞重复顺序DNA研究的一些进展

本文从如下几方面介绍了真核细胞重复顺序DNA结构功能研究的一些进展:(1)串联重复顺序是构成基因多态性的分子基础,基因多态性分析已用于家系分析;(2)一些短的重复顺序如LTR上具有转录调节信号,对基因表达起调控作用;(3)一些重复顺序的表达,与细胞生长分化有一定的相关性;(4)重复顺序在种属演化中具有一定的意义。     

Newly evolved highly repeated DNA sequences ofTupaia glis (Tupaiidae,Scandentia)

We have studied highly repeated DNA sequences ofTupaia glis (Tupaiidae, Scandentia) with restriction endonucleases and Southern blotting techniques. Five highly repeated DNA fragments have been isolated fromT. glis and hybridized with genomic DNAs (cleaved by different restriction enzymes) of several non-human primate species and one insectivore (E. europaeus), in order to highlight eventual differences or similarities of their highly repeated DNA sequences. Our first preliminary findings suggest that the newly isolated highly repeated DNA fragments ofT. glis are distinct from both non-human primates and insectivore, the two taxonomic groups considered most similar to the Tupaiidae.     

Comparison of the restriction endonuclease maps of unintegrated proviral DNAs from four xenotropic murine leukemia viruses.

From purified linear and superhelical DNAs, the restriction endonuclease maps of four xenotropic murine leukemia virus DNAs from NFS, NZB, BALB/c, and AKR mice were determined with ten restriction endonucleases. Each xenotropic proviral DNA was found to be a unique restriction endonuclease map, with differences in the gag, pol, env, and terminal repeated sequence regions. However, type-specific SacI and EcoRI sites in the env region were identical in all four xenotropic murine leukemia virus DNAs and were not found in ecotropic murine leukemia virus DNA. Comparison of the xenotropic murine leukemia virus DNA maps with maps of ecotropic murine leukemia virus DNA showed that the pol and terminal repeated sequence regions were highly conserved. Other similarities in ecotropic and some xenotropic viral DNAs suggest common origins.     

Cloning and characterization of a highly conserved satellite DNA from the mollusc Mytilus edulis.

Sperm DNA of the common mussel, Mytilus edulis, has been found to contain a highly repeated sequence identifiable upon restriction with the endonuclease ApaI. The repetitive nucleotide (nt) sequence amounts to 0.63% of the mollusc genome with an estimated copy number of 5.4 x 10(4) copies per haploid complement. The monomer unit with a 173-bp repeat length has been cloned. Progressive DNA digestions with ApaI yield ladder-like banding patterns on agarose gels, indicating that the repeated elements are tandemly arranged in the genome and therefore represent a sequence of satellite DNA. The degree of internal redundancy of the reiterated sequence is deemed negligible, since nt sequence analysis of a random set of cloned monomers has detected the presence of only a few direct repeats while inverted repeated motifs or any other internal substructures appear absent. The homologies found among cloned monomers are strikingly high, averaging 95%. The results suggest that the exceptional sequence homogeneity of this satellite DNA may be attributed either to some homogenizing mechanism or to evolutionary conserved trends.     

Restriction site periodicities in highly repetitive DNA of primates.

Highly repeated DNA sequences from three Old World primate groups have been compared, using restriction endonucleases. Baboons, macaques and mangabeys share a 340⁴ base-pair, tandemly repeated DNA that is cut once by EndoR · BamHI. The several species of guenons, including the African green monkey, possess a related 170 base-pair, tandemly organized sequence distinguished by the feature of being cut once by EndoR · HindIII, EndoR · MboII or EndoR · HphI. The tandemly repeated DNA of the colobus monkey is based on a monomer length of 680 base-pairs, being cut once by EndoR · BamI or EndoR · EcoRI. Thus, all three highly repeated DNAs have a monomer length of 170n base-pairs, where n = 1, 2 or 4. The 340 and 680 base-pair repeated DNAs contain an internal 170 base-pair periodicity with respect especially to the EndoR · HindIII cleavage site, but with respect also to several other enzymes that characterize each repeated sequence. The 170 base-pair length is called the fundamental unit.The three repeated DNAs are more conserved in the region around the HindIII site and are more divergent elsewhere in the sequence. All seven 170 base-pair fundamental units were related to one another, judging from the overall similarities of the maps of restriction endonuclease cleavage sites. The highly repeated DNAs from baboons and guenons are related enough to cross-hybridize at relaxed criteria (60 °C in 0.12 m-Na⁺) but neither hybridizes to repeated colobus DNA under this condition.The results show that highly repeated sequences in primates form a common library descended from a single ancestral sequence, with 170 base-pairs making up the fundamental unit of library members. Occasionally, a member of the library is amplified, creating a newly amplified family. In Old World monkeys the most recent amplification just preceded active speciation.     

插入序列共同区元件：细菌中新出现的一种基因捕获系统

摘要：插入序列共同区（Insertion sequence common region,ISCR）元件是一类在结构和功能上与IS91家族相似的特殊插入序列,特点是缺少了末端反向重复序列（Inverted repeats, IRs）,在插入位点不产生直接重复序列,并通过滚环式（Rolling circle, RC）进行转座。ISCR元件作为一种新的基因捕获系统,它可以移动邻近的任何DNA序列,为耐药基因在不同种属细菌间水平传播提供了高效的媒介。世界各地多种革兰氏阴性病原菌中已发现有19种ISCR元件,大部分ISCR元件同时携带了多种耐药基因,提示ISCR有可能会造成细菌多重耐药性的快速传播。本文就ISCR结构特征、类型、移动方式、起源及进化的研究进展进行了综述。     

Conservation of repeated DNA base sequences in theCrustacea: A molecular approach to decapod phylogeny

Summary Analysis of data obtained from molecular hybridization of³H-labeled repetitious DNA has been utilized to reconstruct the broad outlines of phylogenetic relationships among decapod Crustacea. This molecular reconstruction agrees reasonably well with the paleontological record, and with other schemes obtained by comparative morphological and serological approaches. Preliminary evidence is in line with the hypothesis that continuous addition of new repeated sequence families to the genome over long periods of time may in part account for the correlation observed between percent repetitious DNA hybridized and divergence time. It is tentatively concluded that a core of DNA base sequence homology has been highly conserved throughout the evolution of theCrustacea. Demonstration of inter-species sequence homology has important implications to models which relegate a genetic regulatory function to repeated DNAs.