Ehret G B, Reichenbach P, Schindler U, Horvath C M, Fritz S, Nabholz M, Bucher P
Swiss Institute for Experimental Cancer Research (ISREC) 1066 Epalinges, Switzerland.
J Biol Chem. 2001 Mar 2;276(9):6675-88. doi: 10.1074/jbc.M001748200. Epub 2000 Oct 26.
STAT transcription factors are expressed in many cell types and bind to similar sequences. However, different STAT gene knock-outs show very distinct phenotypes. To determine whether differences between the binding specificities of STAT proteins account for these effects, we compared the sequences bound by STAT1, STAT5A, STAT5B, and STAT6. One sequence set was selected from random oligonucleotides by recombinant STAT1, STAT5A, or STAT6. For another set including many weak binding sites, we quantified the relative affinities to STAT1, STAT5A, STAT5B, and STAT6. We compared the results to the binding sites in natural STAT target genes identified by others. The experiments confirmed the similar specificity of different STAT proteins. Detailed analysis indicated that STAT5A specificity is more similar to that of STAT6 than that of STAT1, as expected from the evolutionary relationships. The preference of STAT6 for sites in which the half-palindromes (TTC) are separated by four nucleotides (N(4)) was confirmed, but analysis of weak binding sites showed that STAT6 binds fairly well to N(3) sites. As previously reported, STAT1 and STAT5 prefer N(3) sites; however, STAT5A, but not STAT1, weakly binds N(4) sites. None of the STATs bound to half-palindromes. There were no specificity differences between STAT5A and STAT5B.
信号转导和转录激活因子（STAT）转录因子在多种细胞类型中表达，并与相似的序列结合。然而，不同的STAT基因敲除显示出非常不同的表型。为了确定STAT蛋白结合特异性之间的差异是否导致了这些效应，我们比较了STAT1、STAT5A、STAT5B和STAT6所结合的序列。一组序列是通过重组STAT1、STAT5A或STAT6从随机寡核苷酸中筛选出来的。对于另一组包含许多弱结合位点的序列，我们量化了它们对STAT1、STAT5A、STAT5B和STAT6的相对亲和力。我们将结果与其他人鉴定的天然STAT靶基因中的结合位点进行了比较。实验证实了不同STAT蛋白具有相似的特异性。详细分析表明，正如从进化关系所预期的那样，STAT5A的特异性与STAT6的更相似，而与STAT1的不太相似。STAT6对半回文序列（TTC）由四个核苷酸（N(4)）分隔的位点的偏好得到了证实，但对弱结合位点的分析表明，STAT6与N(3)位点结合得相当好。如先前报道的那样，STAT1和STAT5偏好N(3)位点；然而，STAT5A而非STAT1能弱结合N(4)位点。没有一个STAT能结合到半回文序列上。STAT5A和STAT5B之间没有特异性差异。
