抗菌肽的研究及其在植物基因工程中的应用

抗菌肽是一类新型的抗菌物质,在低等生物到高等动植物有广泛分布．抗菌肽及人工合成的抗菌肽基因在植物体中可以被表达并具有杀菌活性,能够应用于植物抗病工程方面,从而提高植物的抗病性．本文简要介绍了抗菌肽的发现、分类、结构、作用机理、基因结构和基因改造,以及抗菌肽在植物基因工程中的应用．     

启动子探针型载体的构建

用ＤＮＡ重组技术构建了启动子探针型系列载体ｐＳＵＰＶ１，ｐＳＵＰＶ２和ｐＳＵＰＶ３，它们是以大肠杆菌质粒载体ｐＢｌｕｅ或ｐＵＣ１８为骨架，ｐＮＧ３５中的卡那霉素抗性（Ｋａｎ＇）基因为标记构建而成。这些载体可用于原核生物、真菌及高等真核生物基因启动子的分离鉴定，并也可用于对已克隆基因启动子的进一步鉴定。     

文昌鱼eIF5A基因的克隆和进化学分析

对文昌鱼神经胚cDNA文库进行测序和系统分析，首次从青岛文昌鱼(Brachiostoma belcheri tsingtauense)中成功得到1个eIFSA基因的cDNA序列，分析其推导的氨基酸序列揭示该基因产物具有eIF-5A家族蛋白质共有的保守区．对其二级结构进行预测，序列同源性分析表明eIF-5A家族基因在所有的真核生物中都高度保守．进化生物学的分析显示文昌鱼的eIF5A基因与脊椎动物的同源性较高，     

基于蛋白质结构的微生物视紫红质系统发生分析

微生物视紫红质是自然界中一类较小的具有7个α螺旋跨膜结构的膜蛋白．目前有功能的微生物视紫红质只发现于单细胞微生物中,但是其分布极为广泛,包括了生物的三界系统．对美国基因数据库（GenBank Database）进行PSI-BLAST搜索后,筛选了38条来自古细菌、细菌和真核生物的视紫红质蛋白质序列并进行了蛋白质结构和序列比对,并对比对结果用了邻接法（Neighbor-joining）和贝叶斯法进行了基于7个α螺旋跨膜结构的系统发生分析．系统发生分析结果表明：这些微生物视紫红质分为3个进化分支,每个分支中按照古细菌,细菌和真核生物的多少可以归类为古细菌类、细菌类和真核生物类微生物视紫红质．虽然这3大类群与生物的三界系统一致,但是每个类群中都混有其他界的微生物视紫红质．水平基因传递可能是导致微生物视紫红质进化上混杂的原因之一．生物的三界系统中都存在微生物视紫红质,说明微生物视紫红质是一种非常古老的基因,其存在可能早于生物三界系统的分化.     

RNAi技术及其在基因组学研究中的应用

RNA干扰（RNA interference,RNAi）是一种真核生物体内的基因调控机制．在介绍RNAi的作用机制及作用特点的基础上,综述了其在基因功能研究、基因组免疫系统、人类疾病的基因治疗及水产养殖病害的防治等基因组学研究领域的最新进展与应用．     

E.coli和Yeast基因起始与终止密码子邻近序列碱基保 …

计算Ｅ．ｃｏｌｉ和Ｙｅａｓｔ基因起始与终止密码子邻近序列单碱基、相邻双碱基、相邻三碱基的碱基出现概率得出的Ｍ１（ｌ）、Ｍ２（ｌ）、Ｍ２（ｌ）值,很好地体现了原核生物Ｅ．ｃｏｌｉ和真核生物Ｙｅａｓｔ翻译起始区域的显著差异;矩阵Ｐ的本征值之和,可作为衡量不同生物基因碱基保守性,关联性强弱强度的一个指标。     

线粒体上核糖核蛋白基因内含子与相应编码序列的相互作用分析

剪切后的内含子对基因的表达调控过程仍发挥着重要的作用,发现内含子通过与相应mRNA的相互作用来实现这些功能的.用改进后的Smith-Waterman算法进行局域比对,对线虫、果蝇、小鼠和人类的线粒体上核糖核蛋白基因的内含子与相应编码序列做匹配性比对分析,发现内含子的中部序列与编码序列存在较强的相互作用,三类内含子上的匹配频率分布显示了各自的特征.在编码序列上有多个最佳匹配区域和禁配区域,推测这些禁配区域可能是蛋白质复合体的结合区域.最佳匹配片段的GC含量分布范围较广,覆盖了其它三类序列分布范围.高等真核生物最佳匹配片段的平均长度比低等真核生物要长一些.结论表明最佳匹配片段的序列特征符合RNA-RNA相互作用的一般规律,内含子应该是一类调控基因表达的功能片段.     

高等真核生物细胞周期蛋白研究进展

综述了高等真核生物细胞周期蛋白的结构及在细胞周期不同时相中的作用，阐明了其对细胞周期调控的机制．     

马铃薯基因文库的构建及贮藏蛋白基因的筛选

以大容量的ＬｏｒｉｓｔＸ为载体，与马铃薯总ＤＮＡ部分酶切产物３０～５０Ｋｂ片段连接，经体外包装和效价测定，得到了６．５×１０５重组克隆，达到了构建马铃薯基因文库的要求．ＬｏｒｉｓｔＸ与ｐｕｃ９质粒可构成筛选目的基因的体内同源重组系统．利用这一系统，经筛选得到了４个目的基因克隆，经分析鉴定，４个克隆的插入片段均含目的基因或其片段．同时也表明这一同源重组系统在真核生物基因筛选方面是有效的．     

着丝粒生物学

着丝粒的关键作用是保证细胞减数分裂和有丝分裂的顺利进行，保证生物的遗传．近年来随着对多个物种的着丝粒测序之后对着丝粒的功能提出了很多相互矛盾的假说．本文阐述了低等真核生物的着丝粒没有重复序列而高等真核生物的着丝粒具有大量的重复序列，并且简述了各物种着丝粒的组成和各类与组蛋白H3、核仁、着丝粒DNA序列及DNA的高级结构相关的着丝粒功能模型．     

Morphogenetic genes C and Nu3 overlap in bacteriophage lambda

In bacteriophage lambda, genes C and Nu3, two of the four cistrons which are essential for normal prohead formation, have overlapping nucleotide sequences. These genes are translated in the same reading frame so that the Nu3 protein is identical to the COOH-terminal one-third of the C protein. This structural relationship may provide for the functional interaction of the C and Nu3 proteins through their regions of structural homology during prohead assembly. The in-phase overlapping organisation of genes may constitute a general strategy to facilitate the mutual interaction of a pair of proteins through their common structural domains.     

Continuum of overlapping clones spanning the entire human chromosome 21q.

A continuous array of overlapping clones covering the entire human chromosome 21q was constructed from human yeast artificial chromosome libraries using sequence-tagged sites as landmarks specifically detected by polymerase chain reaction. The yeast artificial chromosome contiguous unit starts with pericentromeric and ends with subtelomeric loci of 21q. The resulting order of sequence-tagged sites is consistent with other physical and genetic mapping data. This set of overlapping clones will promote our knowledge of the structure of this chromosome and the function of its genes.     

Arrangement of human immunoglobulin heavy chain constant region genes implies evolutionary duplication of a segment containing gamma, epsilon and alpha genes

Cosmid clones containing the human gamma, epsilon and alpha heavy chain constant region genes and an epsilon pseudogene have been isolated. All these genes have a switch sequence detectable by hybridization. We have studied overlapping cosmids covering two separate regions of the genome, and the gene order in each of these regions was found to be gamma-gamma-epsilon-alpha. This implies an evolutionary duplication in this multigene family involving gamma, epsilon and alpha genes.     

A distinct Hox code for the branchial region of the vertebrate head.

The branchial region of the vertebrate head forms through complex interactions involving rhombomeric segments, neural crest and branchial arches. It is though that aspects of their patterning mechanisms are linked and involve Hox-2 genes, whose overlapping and spatially restricted expression domains represent a combinatorial code for generating regional diversity. Vertebrates possess four Hox clusters of Antennapedia class homeobox genes, related to each other by duplication and divergence from a common ancestral complex. In consequence, at equivalent positions in different clusters there are highly related genes known as subfamilies or paralogous groups. As Hox-2 genes cannot fully account for patterning individual rhombomeres, we investigated whether offsets in expression limits of paralogous genes could account for the generation of regional diversity. We report here that, with the exception of the labial subfamily, paralogues show identical expression limits in rhombomeres, cranial ganglia and branchial arches, providing a combinatorial Hox code for the branchial region that seems to be different in organization to that of the trunk.     

The ovalbumin gene region: common features in the organisation of three genes expressed in chicken oviduct under hormonal control.

Two large DNA fragments overlapping the chicken ovalbumin gene have been isolated by molecular cloning. Analysis of these fragments provided a map of a 46,000-base pair region of the chicken genome. This region contains the complete ovalbumin gene (including its mRNA leader-coding sequence) and at least two other genes of unknown function. All three genes are orientated in the same direction and their expression in chicken oviduct is under hormonal control. The three genes share some sequence homologies, suggesting that duplications have occurred in the ovalbumin gene region in the course of evolution.     

Control of neuronal fate by the Drosophila segmentation gene even-skipped

The central nervous system (CNS) contains a remarkable diversity of cell types. The molecular basis for generating this neuronal diversity is poorly understood. Much is known, however, about the regulatory genes which control segmentation and segment identity during early Drosophila embryogenesis. Interestingly, most of the segmentation and homoeotic genes in Drosophila, as well as many of their vertebrate homologues, are expressed during the development of the nervous system (for example, ref. 3). Are these genes involved in specifying the identity of individual neurons during neurogenesis, just as they specify the identity of cells during segmentation? We previously described the CNS expression of the segmentation gene fushi tarazu (ftz) and showed that ftz CNS expression is involved in the determination of an identified neuron. Here we show that another segmentation gene, even-skipped (eve), is expressed in a different but overlapping subset of neurons. Temperature-sensitive inactivation of the eve protein during neurogenesis alters the fate of two of these neurons. Our results indicate that the nuclear protein products of the eve and ftz segmentation genes are components of the mechanism controlling cell fate during neuronal development.     

Coordinate expression of the murine Hox-5 complex homoeobox-containing genes during limb pattern formation

The homoebox-containing genes of the Hox-5 complex are expressed in different but overlapping domains in limbs during murine development. The more 5' the position of these genes in the complex, the later and more distal is their expression. Antero-posterior differences are also observed. A model is proposed that accounts for the establishment of these expression domains in relation to the existence of a morphogen released by the zone of polarizing activity. Comparison of these observations with the expression patterns of the genes of Hox complexes in the early embryo suggests that similar molecular mechanisms are involved in the positional signalling along the axes of both the embryonic trunk and the fetal limbs.     

Hypomethylation-linked activation of PAX2 mediates tamoxifen-stimulated endometrial carcinogenesis

Tamoxifen, a selective oestrogen receptor modulator, has been used in the treatment of all stages of hormone-responsive breast cancer. However, tamoxifen shows partial oestrogenic activity in the uterus and its use has been associated with an increased incidence of endometrial cancer. The molecular explanation for these observations is not known. Here we show that tamoxifen and oestrogen have distinct but overlapping target gene profiles. Among the overlapping target genes, we identify a paired-box gene, PAX2, that is crucially involved in cell proliferation and carcinogenesis in the endometrium. Our experiments show that PAX2 is activated by oestrogen and tamoxifen in endometrial carcinomas but not in normal endometrium, and that this activation is associated with cancer-linked hypomethylation of the PAX2 promoter.