Rathjen J, Mellor J
Department of Biochemistry, University of Oxford, UK.
Nucleic Acids Res. 1990 Jun 11;18(11):3219-25. doi: 10.1093/nar/18.11.3219.
In the phosphoglycerate kinase (PGK) gene of yeast, as in other highly expressed yeast genes, the sequences surrounding the site of RNA initiation have a loosely conserved structure of a CT rich stretch followed by the tetranucleotide CAAG. Using internal deletions and insertions we have identified the elements in the PGK promoter which are required for correct RNA initiation at the CAAG sequence at -39. The results indicate that two different components of the PGK promoter contribute to correct RNA initiation, the TATA homologies, located at -152 and -113, and the sequences at the site of initiation. Both TATA elements can function in RNA initiation. Deletion of the upstream TATA element, TATAI, results in slightly heterogeneous RNA initiation, but the majority of the RNA initiates correctly. Deletion of both the PGK TATA elements results in the majority of the RNA initiating at sites downstream from the wild-type I site, within the structural gene between +40 to +80. The CT rich box is not essential for correct mRNA initiation as shown by deletion analysis. The site of RNA initiation in the PGK promoter appears to be determined by sequences located immediately 5' of the CAAG sequence motif. This short sequence, ACAGATC, when located the correct distance from the TATA elements may be sufficient to determine a discrete initiation site.
在酵母的磷酸甘油酸激酶（PGK）基因中，如同其他高表达的酵母基因一样，RNA起始位点周围的序列具有一种结构松散保守的结构，先是一段富含CT的序列，接着是四核苷酸CAAG。利用内部缺失和插入技术，我们已鉴定出PGK启动子中在-39位的CAAG序列处进行正确RNA起始所需的元件。结果表明，PGK启动子的两个不同组分有助于正确的RNA起始，即位于-152和-113位的TATA同源序列，以及起始位点处的序列。两个TATA元件均可在RNA起始中发挥作用。上游TATA元件TATAI的缺失导致RNA起始略有不均一，但大多数RNA仍能正确起始。PGK的两个TATA元件均缺失会导致大多数RNA在野生型起始位点下游的位点起始，即在结构基因内+40至+80之间。缺失分析表明，富含CT的框对于正确的mRNA起始并非必需。PGK启动子中的RNA起始位点似乎由紧邻CAAG序列基序5'端的序列决定。当该短序列ACAGATC与TATA元件保持正确距离时，可能足以确定一个离散的起始位点。
