Genetic properties and chromatin structure of the yeast gal regulatory element: an enhancer-like sequence.
Genetic properties and chromatin structure of the yeast gal regulatory element: an enhancer-like sequence.
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酵母半乳糖调节元件的遗传特性和染色质结构：增强子样序列。
DOI：
10.1073/pnas.81.24.7865
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发表时间：
1984
影响因子：
11.1
通讯作者：
Struhl,K
中科院分区：
文献类型：
--
作者：
Struhl,K
酵母DNA编码半乳糖调控的上游启动子元件（gal）的365碱基对片段与一组衍生物（系统地删除his3基因上游的序列）融合产生的DNA分子，以单拷贝的形式精确地引入酵母基因组的his3位点，然后进行转录分析。将gal调控元件与含有所有正常mRNA编码序列但基本上缺乏整个启动子区域的his3衍生物融合后，在任何生长条件下都不能表达his3。对缺乏上游启动子元件但含有“TATA盒”的衍生物的融合使his3的表达处于gal控制之下。在含半乳糖的培养基中，RNA水平极高，而在含葡萄糖的培养基中，基本没有his3 RNA。然而，在两个正常的his3起始位点中，只有下游的一个被gal元件激活。在这种类型的融合体中，gal元件的取向和元件与his3 TATA盒之间的距离都不影响转录的水平或起始点。然而，当gal元件位于正常mRNA起始位点下游100或300个碱基对时，它不会影响转录。在葡萄糖生长的细胞中，含有整个his3启动子区域的衍生物的融合恢复了his3转录的基础水平，并且使用了两个转录起始位点。此外，半乳糖培养的细胞中的RNA水平虽然略高于葡萄糖培养的细胞，但明显低于完全诱导的水平。与his3编码序列的距离不影响RNA水平，这表明可能与his3上游启动子元件对应的特定序列降低了gal元件激活转录的能力。对其中一些菌株的染色质分析表明，在gal元件的中间有一个dna酶i超敏位点。然而，这种结构特征与转录起始无关，因为当细胞在葡萄糖培养基中生长时，也在缺乏TATA盒的衍生物中发现。因此，gal上游元件具有高等真核生物的病毒和细胞增强子序列的大部分特性，但不是全部。此外，his3和gal上游序列似乎代表两种不同类型的启动子元件，它们从不同的起始位点激活转录。
DNA molecules created by fusing a 365-base-pair segment of yeast DNA encoding the galactose-regulated upstream promoter element (gal) to a set of derivatives that systematically delete sequences upstream from the his3 gene are introduced in single copy back into the yeast genome precisely at the his3 locus and then assayed for transcription. Fusions of the gal regulatory element to his3 derivatives containing all normal mRNA coding sequences but lacking essentially the entire promoter region fail to express his3 under any growth conditions. Fusions to derivatives lacking the his3 upstream promoter element but containing the "TATA box" place his3 expression under gal control--i.e., extremely high RNA levels in galactose-containing medium and essentially no his3 RNA in glucose-containing medium. However, of the two normal his3 initiation sites, only the downstream one is activated by the gal element. In fusions of this type, neither the orientation of the gal element nor the distance between the element and the his3 TATA box affects the level or the initiation points of transcription. However, the gal element does not influence transcription when placed 100 or 300 base pairs downstream from the normal mRNA start sites. Fusions to derivatives containing the entire his3 promoter region restore the basal level of his3 transcription in glucose-grown cells, and both transcriptional initiation sites are used. Furthermore, RNA levels in galactose-grown cells, although somewhat higher than in glucose-grown cells, are significantly below the fully induced level. The distance from his3 coding sequences does not affect RNA levels, suggesting that specific sequences, possibly corresponding to the his3 upstream promoter element, reduce the ability of the gal element to activate transcription. Analysis of chromatin from some of these strains indicates a DNase I-hypersensitive site(s) in the middle of the gal element. However, this structural feature is not correlated with transcriptional initiation because it is found when cells are grown in glucose medium and also in derivatives lacking a TATA box. Thus, the gal upstream element possesses most, but not all, of the properties of viral and cellular enhancer sequences of higher eukaryotes. In addition, it appears that the his3 and gal upstream sequences represent two distinct classes of promoter elements, which activate transcription from different initiation sites.