Escobar-Henriques Mafalda, Daignan-Fornier Bertrand, Collart Martine A
Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, F-33077 Bordeaux Cedex, France.
Mol Cell Biol. 2003 Sep;23(17):6267-78. doi: 10.1128/MCB.23.17.6267-6278.2003.
Guanylic nucleotides are essential cellular players, and the critical enzyme in their tightly regulated synthesis in Saccharomyces cerevisiae is encoded by the IMD2 gene. The transcription of IMD2 is subject to general repression by nutrient limitation through the cis nutrient-sensing element. It is also subject to specific feedback regulation by the end products of the guanylic nucleotide synthesis pathway. The critical cis element for this latter mechanism is the guanine response element (GRE), a TATAATA sequence which is located 202 nucleotides upstream of the transcription initiation site and which functions as the IMD2 TATA box. We show that the GRE functions in conjunction with a 52-nucleotide stretch near the transcription start site. This very unusual promoter structure ensures low, basal expression of IMD2 and the recruitment of TFIID to the GRE in response to guanylic nucleotide limitation.
鸟苷酸是细胞必需的成分，在酿酒酵母中，其严格调控合成过程中的关键酶由IMD2基因编码。IMD2的转录通过顺式营养感应元件受到营养限制的总体抑制。它还受到鸟苷酸合成途径终产物的特异性反馈调节。后一种机制的关键顺式元件是鸟嘌呤反应元件（GRE），即位于转录起始位点上游202个核苷酸处的TATAATA序列，它作为IMD2的TATA框发挥作用。我们发现，GRE与转录起始位点附近一段52个核苷酸的序列协同发挥作用。这种非常特殊的启动子结构确保了IMD2的低水平基础表达，并在鸟苷酸受限的情况下将TFIID募集到GRE上。
