光/暗对高粱叶片磷酸烯醇式丙酮酸羧化酶基因表达的调节

高粱幼苗黄化叶片经照光转绿后,其PEP-Case活性提高4～15倍,mRNA含量提高了1.03倍,并测定出PEPCase mRNA的分子量为3.4kb。以等量的总RNA及mRNA进行体外翻译,发现转绿后PEPCase专一性翻译活性提高了51％～53％。这表明光照可以在转录水平上调节PEP-Case的基因表达。     

光照对大豆叶片苯丙氨酸裂解酶(PAL)基因表达及异黄酮合成的调节

异黄酮是大豆体内特别是种子中积累的一类重要的次生代谢产物,它具有特殊的生物效能。本实验在不同水平（ＲＮＡ／酶／产物）上研究不同光照条件对大豆叶片异黄酮合成过程中的第一个关键酶苯丙氨酸氨基裂解酶（ＰＡＬ）基因表达的影响。研究发现,在光照条件下ｐａｌ表达量比黑暗条件下高,而且其影响程度与品种有关系,种子中异黄酮含量低的品种表现更敏感;其ｍＲＮＡ的合成受红光、蓝光、紫外光的促进,其中紫外光最有效;随着处     

光照对大豆叶片苯丙氨酸裂解酶(PAL)基因表达及异黄酮合成的调节

异黄酮是大豆体内特别是种子中积累的一类重要的次生代谢产物,它具有特殊的生物效能。本实验在不同水平（RNA/酶/产物）上研究不同光照条件对大豆叶片异黄酮合成过程中的第一个关键酶苯丙氨酸氨基裂解酶（PAL）基因表达的影响。研究发现,在光照条件下pal表达量比黑暗条件下高,而且其影响程度与品种有关系,种子中异黄酮含量低的品种表现更敏感;其mRNA的合成受红光、蓝光、紫外光的促进,其中紫外光最有效;随着处理时间的延长,mRNA的量和酶活性增加;但是在异黄酮的积累水平上,随着紫外光照射时间的延长,表达量有所下降。     

核糖开关与基因表达调控

核糖开关(riboswitch)是近几年基因表达调控研究的一个热点.核糖开关位于mRNA的非翻译区(untranslated regions, UTR),能够直接感受胞内外信号并引起自身二级结构的变化,在转录或后转录（翻译和mRNA稳定性）水平实现对下游相关基因的表达调控,该过程不依赖于包括蛋白质在内的其它任何因子的作用. 根据现已发现的核糖开关所能识别的信号因子类型,可以将其分为4类,即小分子代谢物、金属离子、环境因素及空载tRNA敏感的核糖开关;其中,小分子代谢物敏感的核糖开关是发现和研究最多且最深入的一类. 随着研究的深入,将会有更多的核糖开关被发现,这不仅有助于理解生物进化与环境适应性,而且在生物学基础研究,新型药物的开发以及工业生产领域都将发挥重要作用.     

SREBP介导的基因表达的调控(英文)

SREBP转录因子是脂类代谢的重要调节者。当细胞有脂类需求时,在内质网膜上的SREBP前体通过蛋白水解被激活。然后,氨基端的SREBP片段被运到细胞核内激活靶基因的转录。细胞培养和转基因小鼠模型的研究已经证明,SREBP的主要靶基因包括负责脂肪和胆固醇合成的酶,以及低密度脂蛋白受体。早期对SREBP的研究相当完善地揭示了其前体被激活的机理。最近的研究又使我们认识了细胞核内SREBP的调控机理。在细胞核中,SREBP会结合特定的转录辅助因子,刺激或抑制其靶基因的转录,这些转录辅助因子包括CBP/p300和Mediator蛋白复合体。此外,细胞核内SREBP的稳定性受磷酸化和乙酰化的调节。细胞核内SREBP的这种蛋白质相互作用和修饰,使细胞内外信号(如胰岛素或氧化应激)更好地控制脂类合成。在正常生理状态下,脂质动态平衡是严格保持着的,然而,在有些病理条件下,如肥胖、二型糖尿病、心血管疾病和脂肪肝,SREBP往往会失调。因此,SREBP的新调控机制可能对治疗代谢性疾病提供新的机遇。     

拟南芥非特异性磷脂酶C4基因表达模式的研究

拟南芥非特异性磷脂酶C4（AtNPC4）具有降解磷脂酰胆碱（PC）,产生二酰甘油（DAG）和磷酸胆碱的活性。本研究从拟南芥基因组中分离了NPC4基因起始密码子上游1 379bp的启动子序列,与GUS报告基因融合后转化拟南芥,获得转基因植株。GUS组织化学染色表明,AtNPC4基因主要在处于衰老过程中的叶片中高水平表达,在根、茎、种荚和花中也有一定程度的表达,这种表达模式与RT-PCR结果相一致。另外,通过RT-PCR发现,AtNPC4基因在转录水平上受脱落酸的诱导,但不受水杨酸和茉莉素诱导。     

Dicistronic Gene Expression in Developing Zebrafish

Internal ribosome entry sites (IRESs) allow ribosomal access to messenger RNA without a requirement for cap recognition and subsequent scanning to an initiator AUG. Hence, IRESs have been adapted into dicistronic vectors for the expression of more than one gene from a single mRNA. Dicistronic vectors have been used for many applications in mammalian tissue culture and transgenesis. However, whether the IRESs from mammalian viruses function without temporal or spatial restrictions in nonmammalian organisms like zebra fish (Danio rerio) is unknown. Therefore, we have examined the expression capabilities of the encephalomyocarditis virus (EMCV) IRES during zebrafish embryogenesis. We determined that the EMCV IRES was sufficient to permit detectable expression of several second cistron reporters during zebrafish embryogenesis, including luciferase and green fluorescent protein. This suggests that our dicistronic vectors are suitable for general use in any vertebrate system, from fish to humans. Received March 26, 1999; accepted June 14, 1999.     

Regulation of Expression of Cloned Bacteriophage T4 Late Gene 23

The parameters governing the activity of the cloned T4 gene 23, which codes for the major T4 head protein, were analyzed. Suppressor-negative bacteria carrying wild-type T4 gene 23 cloned into plasmid pCR1 or pBR322 were infected with T4 gene 23 amber phage also carrying mutations in the following genes: (i) denA and denB (to prevent breakdown of plasmid DNA after infection) and (ii) denA, denB, and, in addition, 56 (to generate newly replicated DNA containing dCMP) and alc/unf (because mutations in this last gene allow late genes to be expressed in cytosine-containing T4 DNA). Bacteria infected with these phage were labeled with (14)C-amino acids at various times after infection, and the labeled proteins were separated by one-dimensional gel electrophoresis so that the synthesis of plasmid-coded gp23 could be compared with the synthesis of other, chromosome-coded T4 late proteins. We analyzed the effects of additional mutations that inactivate DNA replication proteins (genes 32 and 43), an RNA polymerase-binding protein (gene 55), type II topoisomerase (gene 52), and an exonuclease function involved in recombination (gene 46) on the synthesis of plasmid-coded gp23 in relation to chromosome-coded T4 late proteins. In the denA:denB:56:alc/unf genetic background, the phage chromosome-borne late genes followed the same regulatory rules (with respect to DNA replication and gp55 action) as in the denA:denB genetic background. The plasmid-carried gene 23 was also under gp55 control, but was less sensitive than the chromosomal late genes to perturbations of DNA replication. Synthesis of plasmid-coded gp23 was greatly inhibited when both the type II T4 topoisomerase and the host's DNA gyrase are inactivated. Synthesis of gp23 was also substantially affected by a mutation in gene 46, but less strongly than in the denA:denB genetic background. These observations are interpreted as follows. The plasmid-borne T4 gene 23 is primarily expressed from a late promoter. Expression of gene 23 from this late promoter responds to an activation event which involves some structural alteration of DNA. In these respects, the requirements for expressing the plasmid-borne gene 23 and chromosomal late genes are very similar (although in the denA:denB:56:alc/unf genetic background, there are significant quantitative differences). For the plasmid-borne gene 23, activation involves the T4 gp46, a protein which is required for DNA recombination. However, for the reasons presented in the accompanying paper (Jacobs et al., J. Virol. 39:31-45, 1981), we conclude that the activation of gene 23 does not require a complete breakage-reunion event which transposes that gene to a later promoter on the phage chromosome. Ways in which gp46 may actually be involved in late promoter activation on the plasmid are discussed.     

籽粒苋中PPDK基因的克隆及表达特性分析

为寻找能提高植物光合效率的基因资源,以高光效植物籽粒苋(Amaranthus hypochondriacus L.)为试材,利用同源克隆和RACE技术克隆了丙酮酸磷酸二激酶(Pyruvate orthophosphate dikinase, PPDK)基因,基因cDNA全长为3 224 bp,其中5′非翻译区为71 bp,阅读框为2 868 bp,3′非翻译区为285 bp,推导的蛋白质为956个氨基酸,分子量约106 kDa。序列分析表明,克隆的基因含有PPDK基因的功能结构域。表达模式分析显示克隆的PPDK基因在绿色组织中特异表达,为PPDK基因的长转录本,初步确定已克隆得到为籽粒苋中的PPDK基因,将其命名为AhPPDK。     

Regulation of Gene Expression in Higher Plants

The study on regulation of gene expression in higher plants has attracted attention of many scientists and is also one of the major scientific research areas in modern biological studies. With advancement of the technology of genetic engineering, more and more details of gene regulation are revealed and it has been found that regulatory zones of most genes are located at the 5' upstream promoter regions. Now,the study on regulation of gene expression is mainly focused on light regulated genes, tissue specific genes, environmental stress induced genes, bormone-induced genes and so on. This article gives a more or less comprehensive review on the several aspects mentioned above.     

植物叶绿体基因组基因表达调控的研究

叶绿体基因的表达在许多方面与原核基因表达相似,所以最早的理论认为叶绿体基因的表达与原核相似,是在转录起始水平上的调控,进一步的研究认为叶绿体基因表达调控是在不同水平上进行的如：转录水平的调节、转录后调节与修饰、翻译和翻译后修饰等。     

miRNA Regulation of Gene Expression: A Predictive Bioinformatics Analysis in the Postnatally Developing Monkey Hippocampus

Regulation of gene expression in the postnatally developing hippocampus might contribute to the emergence of selective memory function. However, the mechanisms that underlie the co-regulation of expression of hundreds of genes in different cell types at specific ages in distinct hippocampal regions have yet to be elucidated. By performing genome-wide microarray analyses of gene expression in distinct regions of the monkey hippocampal formation during early postnatal development, we identified one particular group of genes exhibiting a down-regulation of expression, between birth and six months of age in CA1 and after one year of age in CA3, to reach expression levels observed at 6-12 years of age. Bioinformatics analyses using NCBI, miRBase, TargetScan, microRNA.org and Affymetrix tools identified a number of miRNAs capable of regulating the expression of these genes simultaneously in different cell types, i.e., in neurons, astrocytes and oligodendrocytes. Interestingly, sixty-five percent of these miRNAs are conserved across species, from rodents to humans; whereas thirty-five percent are specific to primates, including humans. In addition, we found that some genes exhibiting greater down-regulation of their expression were the predicted targets of a greater number of these miRNAs. In sum, miRNAs may play a fundamental role in the co-regulation of gene expression in different cell types. This mechanism is partially conserved across species, and may thus contribute to the similarity of basic hippocampal characteristics across mammals. This mechanism also exhibits a phylogenetic diversity that may contribute to more subtle species differences in hippocampal structure and function observed at the cellular level.