Xu H E, Kodadek T, Johnston S A
Department of Internal Medicine, University of Texas-Southwestern Medical Center, Dallas 75235-8573, USA.
Proc Natl Acad Sci U S A. 1995 Aug 15;92(17):7677-80. doi: 10.1073/pnas.92.17.7677.
Most eukaryotic promoters contain multiple binding sites for one or more transcriptional activators that interact in a synergistic manner. A common view is that synergism is a manifestation of the need for many contacts between activators and the general transcription machinery that a single activator presumably cannot fulfill. In this model, various combinations of protein-protein interactions control the level of gene expression. However, we show here that under physiological conditions, a single binding site and presumably GAL4 can activate transcription to the maximum possible level in vivo. Synergistic effects in this natural system are shown to be consistent with cooperative DNA binding. These results point to DNA occupancy as the major element in fine tuning gene expression in the galactose regulon.
大多数真核生物启动子含有一个或多个转录激活因子的多个结合位点，这些激活因子以协同方式相互作用。一种常见观点认为，协同作用是激活因子与通用转录机制之间需要大量接触的体现，而单个激活因子可能无法实现这种接触。在这个模型中，蛋白质 - 蛋白质相互作用的各种组合控制着基因表达水平。然而，我们在此表明，在生理条件下，单个结合位点以及推测的GAL4能够在体内将转录激活到最大可能水平。在这个自然系统中，协同效应被证明与协同DNA结合一致。这些结果表明DNA占据是半乳糖调节子中微调基因表达的主要因素。
