Gray S, Szymanski P, Levine M
Department of Biology, University of California at San Diego, La Jolla 92093-0322.
Genes Dev. 1994 Aug 1;8(15):1829-38. doi: 10.1101/gad.8.15.1829.
Transcriptional repressors play a key role in establishing localized patterns of gene expression in the early Drosophila embryo. Several different modes of repression have been implicated in previous studies, including competition and direct interference with the transcription complex. Here, we present evidence for "quenching," whereby activators and repressors co-occupy neighboring sites in a target promoter, but the repressor blocks the ability of the activator to contact the transcription complex. This study centers on a zinc finger repressor, snail (sna), which represses the expression of neuroectodermal regulatory genes in the presumptive mesoderm. We show that sna can mediate efficient repression when bound 50-100 bp from upstream activator sites. Repression does not depend on proximity of sna-binding sites to the transcription initiation site. sna is not a dedicated repressor but, instead, appears to block disparate activators. We discuss the importance of quenching as a means of permitting separate enhancers to function autonomously within a complex promoter.
转录抑制因子在果蝇早期胚胎中基因表达局部模式的建立过程中发挥着关键作用。先前的研究涉及几种不同的抑制模式，包括竞争以及对转录复合物的直接干扰。在此，我们提供了“淬灭”的证据，即激活因子和抑制因子共同占据目标启动子中的相邻位点，但抑制因子会阻断激活因子与转录复合物接触的能力。本研究聚焦于一种锌指抑制因子——蜗牛蛋白（sna），它在预定中胚层中抑制神经外胚层调节基因的表达。我们发现，当sna结合在距上游激活位点50 - 100个碱基对处时，它能够介导有效的抑制作用。抑制作用并不依赖于sna结合位点与转录起始位点的接近程度。sna并非专门的抑制因子，相反，它似乎能阻断不同的激活因子。我们讨论了淬灭作为一种使不同增强子在复杂启动子内自主发挥功能的方式的重要性。
