Redd M J, Stark M R, Johnson A D
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0414, USA.
Mol Cell Biol. 1996 Jun;16(6):2865-9. doi: 10.1128/MCB.16.6.2865.
It has been proposed that eukaryotic repressors of transcription can act by organizing chromatin, thereby preventing the accessibility of nearby DNA to activator proteins required for transcription initiation. In this study, we test this idea for the yeast alpha 2 repressor using a simple, artificial promoter that contains a single binding site for the activator protein Gal4 and a single binding site for the repressor alpha 2. When both the repressor and the activator are expressed in the same cell, the artificial promoter is efficiently repressed. In vivo footprinting experiments demonstrate that Gal4 can occupy its binding site even when the promoter is repressed. This result indicates that alpha 2-directed repression must result from interference with some stage in transcription initiation other than activator binding to DNA.
有人提出，真核生物转录抑制因子可通过组织染色质发挥作用，从而阻止附近DNA与转录起始所需的激活蛋白接触。在本研究中，我们使用一个简单的人工启动子来验证酵母α2抑制因子的这一观点，该启动子含有一个激活蛋白Gal4的单一结合位点和一个抑制因子α2的单一结合位点。当抑制因子和激活蛋白在同一细胞中表达时，人工启动子会被有效抑制。体内足迹实验表明，即使启动子被抑制，Gal4仍能占据其结合位点。这一结果表明，α2介导的抑制必定是由于干扰了转录起始过程中除激活蛋白与DNA结合之外的某个阶段。
