增强子作用机制研究进展

增强子是能够增强启动子转录活性的ＤＮＡ顺式作用序列。增强子的结构与启动子相似,也是由多个元件组成,每个元件可以与一种或多种转录调控因子结合。增强子可以在启动子区的上游或下游起增强转录作用且与其距转录起点的远近无关。如Ｔ细胞受体α链基因的增强子位于启动...     

Y—box结合蛋白的研究进展

Y-box元件是指存在于一些基因的启动子或增强子中的一类顺式调控元件。其核心序列为“CCAAT”。对一些基因启动子中的CCAAT序列进行点突变和基因缺失的实验,证实这个顺式调控元件在基因转录调控中扮演重要角色。自1987年以来,人们从不同种类细胞核内检测到多种能与CCAAT元件结合的因子,如人类组织细胞中的CTF、NPI、YB1、CBP、CP1、CP2、dbp1、dbpB;大鼠及其他一些     

组织和发育特异性基因的远距离转录调控

远距离转录调控是指增强子、沉默子和隔离子等顺式作用元件参与的组织和发育特异性基因的表达调控。其调控元件可位于距转录基因很远的DNA区域,甚至分布于邻近基因内含子中。随着人类基因组计划和各种模式生物测序工作的完成,为大规模快速查找远距离调控元件提供了新的手段。由于基因组结构的复杂性,很难建立统一的基因表达调控模型,目前认为启动子与增强子的相互作用是组织和发育特异性基因成功表达的关键。另外,远距离转录调控机制一旦破坏还将导致疾病的发生。     

NGAL基因不同长度片段的克隆及其顺式作用元件定位分析

NGAL(neutrophilgelatinase-associatedlipocalin)是lipocalin家族的一个新成员,可能是人类的一种新癌基因,但其在肿瘤中的表达调控机制尚不清楚。应用生物信息学手段对NGAL(X99133,包括外显子和内含子)进行分析发现,此区域内含有许多潜在的顺式作用元件,其中主要为增强子元件。对此设计了以下实验:应用PCR技术从食管癌细胞SHEEC基因组DNA中扩增不同长度的NGAL基因片段,将其连接到PGEMT-eacy载体中进行扩增,并测序。NCBI/BLAST分析确认扩增片段为NGAL基因所有,与实验所设计相吻合。在此基础上并应用KEGG/MOTIF检索分析系统对NGAL基因的上述区段进行了顺式作用元件定位分析,结果共鉴定出5个Score值=100分的顺式作用元件位点。这为NGAL基因增强子的鉴定提供了新线索。     

原核增强子样序列研究进展

增强子是真核细胞中增强启动子功能的顺式作用元件。随着人们对原核生物基因表达调控的深入研究,人们发现在原核生物的调控系统和某些病毒基因组DNA片段中也具有增强子样功能。这些研究对揭示原核系统的基因表达调控和增强外源基因在原核系统中的表达水平具有重要的理论意义和实用价值。     

植物非生物胁迫诱导启动子顺式作用元件的研究方法

非生物胁迫严重影响植物生长发育,降低作物产量。植物通过各种途径忍受或抵抗非生物胁迫,主要表现是各种抗非生物胁迫基因的表达。基因表达受其上游启动子及转录因子的调控,目前对抗非生物胁迫诱导启动子顺式作用元件及转录因子的研究成为热点。本文综述了植物非生物胁迫诱导启动子顺式作用元件及转录因子的研究方法,并展望了顺式作用元件及转录因子研究的方向及前景。     

再生调控的开关:组织再生增强子的研究进展

再生是组织发生损伤后恢复原有形态和功能的过程。不同脊椎动物的再生能力差异很大,硬骨鱼和两栖动物再生能力很强,而哺乳动物的再生能力极其有限。不同物种再生能力的差异很可能不是由于再生特异基因在进化过程中丢失造成的,相反,调控元件在组织损伤时的激活与否可能是决定再生成功与否的开关。增强子是一种顺式作用调控元件,对于精确调控基因表达必不可少。目前已经在多种模式生物中鉴定出了多个组织再生增强子,并报道了这些元件在组织再生中的关键作用。这篇综述将重点介绍增强子在组织再生中的重要调控作用,组织再生增强子的预测和鉴定,以及组织再生增强子在损伤时被激活的具体机制。     

增强子功能鉴定及其在农业动物中的研究进展

真核生物的基因转录受多种元件共同调控,其中增强子是重要的顺式作用元件,能够极大促进基因的转录。增强子的功能与细胞、组织、个体的特异性功能或表型密切相关,其异常功能往往导致性状改变和疾病发生。因此,研究增强子的功能对于揭示表型背后的分子机理具有十分重要的生物学意义,对于农业动物科学显得尤为重要。本文就增强子的特性、鉴定方法、活性检测以及在农业动物研究中的进展进行综述,以期能够对增强子的相关研究提供依据和参考。     

植物非生物胁迫诱导启动子顺式元件及转录因子研究进展

顺式作用元件(cix-acting element)是与结构基因串联的特定DNA序列,是转录因子的结合位点,它们通过与转录因子结合调控基因转录的精确起始和转录效率,在植物基因表达调控过程中起着重要的作用.非生物胁迫诱导基因的表达受其上游启动子顺式作用元件及转录因子的调控,目前已发现了多种与非生物胁迫相关的顺势作用元件及转录因子,如DRE元件及DREB类转录因子、MYB元件及MYB类转录因子、GT-1元件及GT-1类转录因子等.顺式作用元件及转录因子的研究对研究植物非生物胁迫相关基因的表达调控具有重要意义,综述植物非生物胁迫诱导启动子功能元件及转录因子的研究进展.     

增强子及其生物信息学预测

真核生物基因表达调控是当代分子生物学研究的重要课题之一。增强子是主要的真核生物基因表达调控的顺式作用元件,能有效促进基因表达。因此,增强子的相关研究是当今分子生物学研究的重点之一。运用生物信息学方法具有方便、快捷以及成本低等优势,这使得生物信息学成为当代分子生物学研究的重要工具。本文简单综述了增强子相关研究进展和采用生物信息学策略对序列保守性增强子进行预测和定位的几个常用数据库和具体方法。     

Blockers and barriers to transcription: competing activities?

In the eukaryotic cell active and inactive genes reside adjacent to one another and are modulated by numerous regulatory elements. Insulator elements prevent the misregulation of adjacent genes by restricting the effects of the regulatory elements to specific domains. Enhancer blockers prevent enhancers from inadvertently activating neighboring genes, and recent results suggest that they might function by a conserved mechanism across species. These elements appear to disrupt enhancer-promoter "communications" by interacting with the regulatory elements and sequestering these elements into specific regions of the nucleus thus rendering them non-functional. Barrier elements insulate active genes from neighboring heterochromatin and recent results suggest that they function by specific localized recruitment of acetyltransferases that antagonize the spread of heterochromatin-associated deacetylases, thus preventing the propagation of heterochromatin.     

Bovine umbilical hernia maps to the centromeric end of Bos taurus autosome 8

Twelve bull calves were produced by mating elite Israeli cows to "Glenhapton Enhancer", a Canadian Holstein bull. The frequency of umbilical hernia (UH) in the progeny of the sons ranged from 1 to 21%, consistent with the hypothesis that Enhancer is the carrier of major dominant or codominant gene with partial penetrance for UH. Five sons of Enhancer produced progeny with >10% frequency of UH including sire 3259, whereas progeny of three sons had <3% UH. A total of 116 grand-progeny of Enhancer, all progeny of 3259, were genotyped for 59 microsatellites spanning the 29 bovine autosomes. Of these offspring, 41 were affected. Significant differences in paternal allele frequencies between the affected and unaffected progeny groups were found for marker BMS1591 on bovine chromosome 8 (BTA8). The UH-associated paternal allele originated from Enhancer. The chromosomal segment associated with UH was more precisely mapped between UWCA47, on the centromeric end of BTA8 and RM321, 12 cM from the centromere. A maximum LOD score of 3.84 was obtained 2.5 cM from the centromere with a support interval of 8 cM. Haplotype analysis of eight sons of Enhancer suggested that the UH gene is located in the centromeric end of BTA8 beyond ARO71/ARO72. Thus, by integrating the results from progeny of sire 3259 and sons of Enhancer the location of the UH gene was further refined to the BTA8 segment between ARO71/ARO72 and UWCA47.     

A Note on the Maternal Effect Mutants Daughterless and Abnormal Oocyte in DROSOPHILA MELANOGASTER

Two deficiencies for, and a dominant enhancer of, the second chromosome maternal effect mutant, "daughterless" (da), were induced with X-irradiation. Their properties were studied with respect to both da and the linked maternal effect mutant, "abnormal oocyte" (abo), with the following conclusions. (1) The most probable map positions of da and abo are: J-(1/2)-da-2(1/2)-abo, where J is a dominant marker located at 41 on the standard map. (2) The da locus is in bands 31CD-F on the polytene chromosome map; abo is to the right of 32A. (3) Because homozygous da individuals survive while individuals carrying da and a deficiency for da are lethal, it is concluded that da is hypomorphic. (4) From a weak da-like maternal effect in heterozygous da females induced by an "Enhancer of da," we have confirmed a previous report that (a) the amount of sex chromosome heterochromatin contributed by the father can influence the severity of the da maternal effect, and (b) the sex chromosome heterochromatin which influences the da effect is different from that which influences the abo effect. (5) The possibility that da and abo are in a special region of chromosome 2 concerned with the regulation of sex chromosome heterochromatin is strengthened by the observation that the Enhancer of da appears to rescue abnormal eggs produced by homozygous abo mothers. (6) The Enhancer of da is a translocation between chromosomes 2 and 3 with the second chromosome breakpoint in the basal heterochromatin; because the enhancing effect maps in this region of chromosome 2, it is possible that autosomal, as well as sex chromosomal, heterochromatin interacts with da and abo.     

Chromatin domains, insulators, and the regulation of gene expression

The DNA sequence elements called insulators have two basic kinds of properties. Barrier elements block the propagation of heterochromatic structures into adjacent euchromatin. Enhancer blocking elements interfere with interaction between an enhancer and promoter when placed between them. We have dissected a compound insulator element found at the 5' end of the chicken β-globin locus, which possesses both activities. Barrier insulation is mediated by two kinds of DNA binding proteins: USF1/USF2, a heterodimer which recruits multiple enzyme complexes capable of marking histone on adjacent nucleosomes with 'activating' marks, and Vezf1, which protects against DNA methylation. We have found that the heterochromatic region upstream of the insulator element is maintained in its silent state by a dicer-dependent mechanism, suggesting a mechanism for Vezf1 function in the insulator. Enhancer blocking function in the β-globin insulator element is conferred by a binding site for CTCF. Consistent with this property, CTCF binding was found some years ago to be essential for imprinted expression at the Igf2/H19 locus. Work in many laboratories has since demonstrated that CTCF helps stabilize long-range interactions in the nucleus. We have recently shown that in the case of the human insulin locus such an interaction, over a distance of ~300kb, can result in stimulation of a target gene which itself is important for insulin secretion. This article is part of a Special Issue entitled: Chromatin in time and space.