Struhl K
Proc Natl Acad Sci U S A. 1985 Dec;82(24):8419-23. doi: 10.1073/pnas.82.24.8419.
pet56, his3, and ded1 are adjacent but unrelated genes located on chromosome XV of the yeast Saccharomyces cerevisiae. his3 and pet56 are transcribed in opposite directions from initiation sites separated by approximately equal to 200 base pairs. Under normal growth conditions, both genes are transcribed at a similar basal level. Deletion analysis of the his3 gene indicates that the upstream promoter element for constitutive expression is defined by a 17-base-pair region that contains 15 thymidine residues in the coding strand. Sequential deletions of the pet56 gene indicate that this same region is required for wild-type transcription levels. Thus, this poly(dA-dT) sequence acts bidirectionally to activate transcription of two unrelated genes. Transcription of the ded1 gene is initiated approximately equal to 300 base pairs downstream from the his3 gene, and it occurs at a 5-fold higher level. This gene contains a 34-base-pair region containing 28 thymidine residues in the coding strand located upstream from the ded1 TATA box. Deletion of this dA-dT stretch significantly reduces transcription below the wild-type level. Thus, for at least three different yeast genes, naturally occurring stretches of poly(dA-dT) serve as upstream promoter elements for constitutive expression. In addition, it appears that longer stretches of poly(dA-dT) are more effective upstream promoter elements. These transcriptional effects may be due to exclusion of nucleosomes from poly(dA-dT) regions.
pet56、his3和ded1是相邻但不相关的基因，位于酿酒酵母的第十五号染色体上。his3和pet56从起始位点开始以相反方向转录，起始位点相隔约200个碱基对。在正常生长条件下，这两个基因都以相似的基础水平转录。对his3基因的缺失分析表明，组成型表达的上游启动子元件由一个17个碱基对的区域定义，该区域在编码链中包含15个胸腺嘧啶残基。对pet56基因的连续缺失表明，野生型转录水平需要相同的区域。因此，这个聚（dA-dT）序列双向作用以激活两个不相关基因的转录。ded1基因的转录起始于his3基因下游约300个碱基对处，其转录水平高5倍。该基因在ded1 TATA框上游的编码链中包含一个34个碱基对的区域，其中有28个胸腺嘧啶残基。删除这个dA-dT片段会使转录显著降低至野生型水平以下。因此，对于至少三个不同的酵母基因，天然存在的聚（dA-dT）片段作为组成型表达的上游启动子元件。此外，似乎更长的聚（dA-dT）片段是更有效的上游启动子元件。这些转录效应可能是由于核小体从聚（dA-dT）区域被排除。
