Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
BMC Mol Biol. 2010 Jan 13;11:2. doi: 10.1186/1471-2199-11-2.
The GLI transcription factors, mediators of the hedgehog signal bind with high affinity to the consensus sequence GACCACCCA. The affinity of variant single substitutions in GLI binding sites has been measured systematically, but the affinities of the variant binding sites appears low compared to the frequency of occurrence of variant sites in known GLI target gene promoters.
We quantified transcriptional activation by GLI using PTCH1 promoter based luciferase reporters containing all single substitutions of the GLI consensus binding site. As expected variants with very low affinity did not activate the reporter. Many lower affinity binding sequences are, however, functional in the presence of moderate GLI concentration. Using two natural non-consensus GLI site promoters we showed that substitution of the variant sequences by consensus leads to comparable activity.
Variant GLI binding sites with relatively low affinity can within natural promoters lead to strong transcriptional activation. This may facilitate the identification of additional direct GLI target genes.
GLI 转录因子是 hedgehog 信号的介质，与高亲和力结合到 GLI 结合位点的共识序列 GACCACCCA。GLI 结合位点的变体单取代的亲和力已被系统地测量，但与已知 GLI 靶基因启动子中变体位点的出现频率相比，变体结合位点的亲和力似乎较低。
我们使用含有 GLI 共识结合位点所有单取代的基于 PTCH1 启动子的荧光素酶报告基因来量化 GLI 的转录激活。如预期的那样，亲和力非常低的变体不能激活报告基因。然而，许多较低亲和力的结合序列在存在中等 GLI 浓度的情况下是有功能的。使用两个天然非共识 GLI 位点启动子，我们表明通过共识取代变体序列可导致相当的活性。
具有相对较低亲和力的变体 GLI 结合位点可以在天然启动子中导致强烈的转录激活。这可能有助于鉴定更多的直接 GLI 靶基因。
