Villain P, Mache R, Zhou D X
Laboratoire de Génétique Moléculaire des Plantes, Unité Mixte de Recherche-5575, Centre National de la Recherche Scientifique, Université de Grenoble 1, 38041 Grenoble cédex, France.
J Biol Chem. 1996 Dec 20;271(51):32593-8. doi: 10.1074/jbc.271.51.32593.
Promoter studies have revealed that sequences related to the GT-1 binding site, known as GT elements, are conserved in plant nuclear genes of diverse functions. In this work, we addressed the issue of whether GT elements are involved in cell type-specific transcriptional regulation. We found that the inactivation of GT-1 site-mediated transcription in roots is correlated with the absence of the GT-1 binding activity in root extracts. In addition, the mutation of the related GT-1 (from the pea rbcs-3A) and the S1F (from the spinach rps1) sites resulted in an increase of their transcriptional activity in roots that contain a distinct GT element-binding factor, referred to as RGTF. Although specific to GT elements, RGTF has a different sequence requirement and a lower sequence specificity than GT-1. Interestingly, RGTF has a higher binding affinity to the mutant GT-1 and S1F sites than to the wild-type sequences. This correlation suggests that RGTF may have some role in transcriptional regulation in roots. Furthermore, root cellular protein extracts contain an inhibitory activity that prevents GT-1 from binding to DNA. This helps to explain the absence of the GT-1 binding activity in roots in which the gene of GT-1 is expressed. Together, these data suggest that the cell type-specific transcription modulation by GT elements is achieved by using two different strategies.
启动子研究表明，与GT-1结合位点相关的序列（称为GT元件）在功能多样的植物核基因中是保守的。在这项研究中，我们探讨了GT元件是否参与细胞类型特异性转录调控这一问题。我们发现，根中GT-1位点介导的转录失活与根提取物中缺乏GT-1结合活性相关。此外，相关GT-1（来自豌豆rbcs-3A）和S1F（来自菠菜rps1）位点的突变导致它们在含有一种独特的GT元件结合因子（称为RGTF）的根中的转录活性增加。尽管RGTF对GT元件具有特异性，但它与GT-1相比具有不同的序列要求和较低的序列特异性。有趣的是，RGTF对突变的GT-1和S1F位点的结合亲和力高于对野生型序列的结合亲和力。这种相关性表明RGTF可能在根的转录调控中发挥某种作用。此外，根细胞蛋白提取物含有一种抑制活性，可阻止GT-1与DNA结合。这有助于解释在表达GT-1基因的根中缺乏GT-1结合活性的现象。总之，这些数据表明，GT元件通过两种不同的策略实现细胞类型特异性转录调控。
