Gaudreau L, Keaveney M, Nevado J, Zaman Z, Bryant G O, Struhl K, Ptashne M
Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA.
Proc Natl Acad Sci U S A. 1999 Mar 16;96(6):2668-73. doi: 10.1073/pnas.96.6.2668.
The idea that recruitment of the transcriptional machinery to a promoter suffices for gene activation is based partly on the results of "artificial recruitment" experiments performed in vivo. Artificial recruitment can be effected by a "nonclassical" activator comprising a DNA-binding domain fused to a component of the transcriptional machinery. Here we show that activation by artificial recruitment in yeast can be sensitive to any of three factors: position of the activator-binding elements, sequence of the promoter, and coding sequences downstream of the promoter. In contrast, classical activators worked efficiently at all promoters tested. In all cases the "artificial recruitment" fusions synergized well with classical activators. A classical activator evidently differs from a nonclassical activator in that the former can touch multiple sites on the transcriptional machinery, and we propose that that difference accounts for the broader spectrum of activity of the typical classical activator. A similar conclusion is reached from studies in mammalian cells in the accompanying paper [Nevado, J., Gaudreau, L., Adam, M. & Ptashne, M. (1999) Proc. Natl. Acad. Sci. USA 96, 2674-2677].
转录机制被招募到启动子上就足以激活基因，这一观点部分基于在体内进行的“人工招募”实验结果。人工招募可通过一种“非经典”激活剂来实现，该激活剂由与转录机制的一个组分融合的DNA结合结构域组成。在此我们表明，酵母中通过人工招募实现的激活可能对三个因素中的任何一个敏感：激活剂结合元件的位置、启动子的序列以及启动子下游的编码序列。相比之下，经典激活剂在所有测试的启动子上都能有效发挥作用。在所有情况下，“人工招募”融合物都能与经典激活剂很好地协同作用。经典激活剂显然与非经典激活剂不同，前者可以接触转录机制上的多个位点，我们认为这种差异解释了典型经典激活剂更广泛的活性谱。在随附论文中对哺乳动物细胞的研究也得出了类似结论[内瓦多，J.，高德罗，L.，亚当，M. & 普塔什内，M.（1999年）《美国国家科学院院刊》96，2674 - 2677]。
