人B细胞活化因子基因启动子活性研究

为探索与自身免疫病发病密切相关的B细胞活化因子(BAFF)基因高水平转录的启动序列及IFN-γ等炎性细胞因子对其活性的影响,以人BAFF基因转录起始点上游-1 349 bp至-329 bp的片段为靶序列,取长度不等的片段作为启动子与含氯霉素乙酰基转移酶(CAT)报告基因的质粒组成5个重组体,脂质体转染法转染上述重组体至人骨髓白血病细胞株:HL-60,CAT-ELISA测定细胞CAT表达水平以比较各重组体的启动子活性;同时加入细胞因子IL-10、IFN-γ、IL-4、重组人BAFF蛋白(rBAFF),以测定其对BAFF启动序列的影响。结果表明,-1 349~-329 bp、-1 349~-743 bp序列具有强启动调控活性,而-1 349~-1 099 bp片段启动活性最低。细胞因子IFN-γ、IL-10和rBAFF均能在一定程度上调人BAFF基因的启动活性,IL-4则一定程度地抑制BAFF基因的启动活性。研究提示,人BAFF基因-1349~-743 bp片段是进一步研究BAFF基因转录相关DNA结合蛋白的重要调控靶序列。细胞因子IL-10、IFN-γ、IL-4、rBAFF可以一定程度的在转录水平影响BAFF合成和分泌。     

Nucleotide sequence and transcriptional regulation of a positive regulatory gene of Shigella dysenteriae.

A 1,937 bp PstI-HindIII fragment containing the ipaR locus was cloned from the large invasion plasmid of Shigella dysenteriae CG097, and its nucleotide sequence was completely determined. The IpaR protein (35 kDa, calculated from the DNA sequence) was synthesized in Escherichia coli chi 1411 minicells containing the 1,937-bp PstI-HindIII fragment. To determine the regulatory role of ipaR for ipa genes, we applied genetic complementation experiments using chloramphenicol acetyltransferase (CAT) as reporter. Analyses of CAT activity of the recombinant plasmids containing the 5' flanking sequences of the 24-kDa-protein gene and the ippI, ipaB, ipaC, and ipaD genes defined strong promoters upstream of the 24-kDa-protein gene and ipaD gene, weak promoters upstream of the ippI and ipaB genes, and the absence of any promoter activity for the ipaC gene. Complementation analyses showed that the CAT activity only under direction of the ippI promoter region increased 1.8-fold in the presence of IpaR protein. On the basis of our data, we suggest that an operon comprising ippI, ipaB, and ipaC is positively regulated by IpaR protein which has a trans effect on a DNA sequence upstream of the ippI promoter.     

人朊蛋白基因外显子Ⅰ及其上游序列具有启动子样活性

目的 鉴定朊蛋白（ＰｒＰ）基因转录启动子位置。方法 利用聚合酶链反应（ＰＣＲ）扩增人ＰｒＰ基因外显子Ⅰ及其上游序列，序列鉴定后插入ＣＡＴ报道质粒ｐＢＬ－ＣＡＴ６，分别转染ＨｅＬａ、ＣＯＳ７和Ｓｈ－ｓｙ５ｙ细胞系，检测ＣＡＴ表达值；提取三种细胞蛋白，以条带移动实验检测细胞转录激活因子ＳＰ１含量。结果 人ＰｒＰ基因外显子Ｉ及其上游序列为ＧＣ富含，带有多个ＳＰ１可能性综合位点，但无明显ＴＡＴＡ盒；瞬时转染结果显示这段序列可诱导２～３倍的ＣＡＴ表达增强；定量移动条带实验证明ＨｅＬａ细胞中含有较高浓度的ＳＰ１，而ＣＯＳ７和Ｓｈ－ｓｙ５ｙ细胞中ＳＰＩ含量极低。结论 人ＰｒＰ基因外显子Ｉ及其上游序列具有启动子样功能，为弱的非ＴＡＴＡ盒启动子；不同组织来源的细胞中ＳＰ１含量不同，在神经细胞系Ｓｈ－ｓｙ５ｙ中人ＰｒＰ基因外显子Ｉ     

Evidence for a complex regulatory array in the first intron of the human adenosine deaminase gene

Adenosine deaminase (ADA) is expressed ubiquitously by diverse mammalian cells and tissues but at levels that vary according to tissue and species. In humans, the thymus exhibits levels of the enzyme up to 100-fold higher than most other tissues. Using transgenic mice, we identified human ADA gene regulatory domains. Up to 3.7 kb of 5'-flanking and first exon DNA from the human ADA gene failed to promote the expression of a chloramphenicol acetyl transferase (CAT) reporter gene in an efficient, reproducible, or tissue-appropriate manner in transgenic mice. However, when 12.8 kb of DNA from the first intron of the human ADA gene was placed 3' of CAT-coding and -processing sequences, transgenic mice reproducibly expressed CAT activity in most tissues, with profoundly high levels in the thymus. DNase I hypersensitivity studies demonstrated that among transgenic mouse tissues, human thymus, and a variety of human cell lines, a region of the intron 4-10 kb downstream of the first exon exhibited an array of hypersensitive sites that varied according to tissue and cell type. Deletion of this region from the gene construction eliminated high-level expression in transgenic mice. In transfection-transient expression assays, the 12.8-kb intron fragment exhibited enhancer activity in several cell types. A 1.3-kb fragment encompassing two of the hypersensitive sites exhibited some of these activities. The results of these studies suggest that the diverse pattern of human ADA gene expression is determined, in part, by a cluster of cis-regulatory elements contained within its large first intron.