Janson L, Pettersson U
Department of Medical Genetics, Uppsala University, Sweden.
Proc Natl Acad Sci U S A. 1990 Jun;87(12):4732-6. doi: 10.1073/pnas.87.12.4732.
We have examined whether the functional synergism between transcription factors Sp1 and OTF-1 involves cooperativity in binding. To demonstrate cooperativity, synthetic enhancers were constructed in which Sp1-binding sites were combined with various OTF-1-binding sites that differed in their binding affinities. The ability of these constructions to activate transcription from the human U2 small nuclear RNA promoter was measured. The results showed that an Sp1-binding site stimulated transcription 2-fold when combined with a high-affinity binding site for OTF-1. When combined with a low-affinity OTF-1-binding site, in contrast, a 20-fold stimulation of transcription was observed. The stimulatory effect of Sp1 was moreover influenced by the distance between the Sp1- and OTF-1-binding sites and the functional cooperation was mirrored by the cooperative formation of OTF-1- and Sp1-specific protein-DNA complexes in vitro. We conclude from these results that the functional cooperation between OTF-1 and Sp1 involves physical interactions between the two transcription factors resulting in cooperative binding. The results thus reveal a mechanism by which Sp1 can modulate transcription.
我们研究了转录因子Sp1和OTF-1之间的功能协同作用是否涉及结合方面的协同性。为了证明协同性，构建了合成增强子，其中Sp1结合位点与结合亲和力不同的各种OTF-1结合位点相结合。测定了这些构建体激活人U2小核RNA启动子转录的能力。结果表明，当Sp1结合位点与OTF-1的高亲和力结合位点结合时，可刺激转录2倍。相反，当与低亲和力的OTF-1结合位点结合时，观察到转录被刺激20倍。此外，Sp1的刺激作用受Sp1和OTF-1结合位点之间距离的影响，并且体外OTF-1和Sp1特异性蛋白质-DNA复合物的协同形成反映了功能协同作用。我们从这些结果得出结论，OTF-1和Sp1之间的功能协同作用涉及两种转录因子之间的物理相互作用，从而导致协同结合。因此，这些结果揭示了Sp1调节转录的机制。
