Stockinger E J, Gilmour S J, Thomashow M F
Department of Crop and Soil Sciences, Michigan State University, East Lansing 48824, USA.
Proc Natl Acad Sci U S A. 1997 Feb 4;94(3):1035-40. doi: 10.1073/pnas.94.3.1035.
Recent efforts have defined a cis-acting DNA regulatory element in plants, the C-repeat/dehydration responsive element (DRE), that stimulates transcription in response to low temperature and water deficit. Here we report the isolation of an Arabidopsis thaliana cDNA that encodes a C-repeat/DRE binding factor, CBF1 (C-repeat/DRE Binding Factor 1). Analysis of the deduced CBF1 amino acid sequence indicates that the protein has a molecular mass of 24 kDa, a potential nuclear localization sequence, and a possible acidic activation domain. CBF1 also has an AP2 domain, which is a DNA-binding motif of about 60 aa present in the Arabidopsis proteins APETALA2, AINTEGUMENTA, and TINY; the tobacco ethylene response element binding proteins; and numerous other plant proteins of unknown function. The transcript levels for CBF1, which appears to be a single or low copy number gene, did not change appreciably in plants exposed to low temperature or in detached leaves subjected to water deficit. Binding of CBF1 to the C-repeat/DRE was demonstrated in gel shift assays using recombinant CBF1 protein expressed in Escherichia coli. Moreover, expression of CBF1 in yeast was found to activate transcription of reporter genes containing the C-repeat/DRE as an upstream activator sequence but not mutant versions of the DNA element. We conclude that CBF1 can function as a transcriptional activator that binds to the C-repeat/DRE DNA regulatory element and, thus, is likely to have a role in cold- and dehydration-regulated gene expression in Arabidopsis.
最近的研究工作确定了植物中的一种顺式作用DNA调控元件，即C重复/脱水响应元件（DRE），它能响应低温和水分亏缺刺激转录。在此，我们报道了拟南芥一个编码C重复/DRE结合因子CBF1（C重复/DRE结合因子1）的cDNA的分离。对推导的CBF1氨基酸序列的分析表明，该蛋白质分子量为24 kDa，有一个潜在的核定位序列和一个可能的酸性激活结构域。CBF1还具有一个AP2结构域，这是一个约60个氨基酸的DNA结合基序，存在于拟南芥蛋白质APETALA2、AINTEGUMENTA和TINY中；烟草乙烯反应元件结合蛋白；以及许多其他功能未知的植物蛋白中。CBF1似乎是一个单拷贝或低拷贝数基因，其转录水平在暴露于低温的植物或水分亏缺的离体叶片中没有明显变化。使用在大肠杆菌中表达的重组CBF1蛋白，通过凝胶迁移试验证明了CBF1与C重复/DRE的结合。此外，发现CBF1在酵母中的表达可激活含有C重复/DRE作为上游激活序列的报告基因的转录，但不能激活该DNA元件的突变体版本。我们得出结论，CBF1可作为一种转录激活因子，与C重复/DRE DNA调控元件结合，因此可能在拟南芥的冷调节和脱水调节基因表达中发挥作用。
