Soldaini E, John S, Moro S, Bollenbacher J, Schindler U, Leonard W J
Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, Maryland 20892, USA.
Mol Cell Biol. 2000 Jan;20(1):389-401. doi: 10.1128/MCB.20.1.389-401.2000.
We have defined the optimal binding sites for Stat5a and Stat5b homodimers and found that they share similar core TTC(T/C)N(G/A)GAA interferon gamma-activated sequence (GAS) motifs. Stat5a tetramers can bind to tandemly linked GAS motifs, but the binding site selection revealed that tetrameric binding also can be seen with a wide range of nonconsensus motifs, which in many cases did not allow Stat5a binding as a dimer. This indicates a greater degree of flexibility in the DNA sequences that allow binding of Stat5a tetramers than dimers. Indeed, in an oligonucleotide that could bind both dimers and tetramers, it was possible to design mutants that affected dimer binding without affecting tetramer binding. A spacing of 6 bp between the GAS sites was most frequently selected, demonstrating that this distance is favorable for Stat5a tetramer binding. These data provide insights into tetramer formation by Stat5a and indicate that the repertoire of potential binding sites for this transcription factor is broader than expected.
我们已经确定了Stat5a和Stat5b同型二聚体的最佳结合位点，发现它们共享相似的核心TTC(T/C)N(G/A)GAA干扰素γ激活序列（GAS）基序。Stat5a四聚体可以结合串联连接的GAS基序，但结合位点选择显示，在许多非一致性基序中也能观察到四聚体结合，而在很多情况下这些基序不允许Stat5a以二聚体形式结合。这表明与二聚体相比，允许Stat5a四聚体结合的DNA序列具有更大程度的灵活性。实际上，在一个既能结合二聚体又能结合四聚体的寡核苷酸中，可以设计出影响二聚体结合而不影响四聚体结合的突变体。GAS位点之间最常选择的间隔是6个碱基对，这表明这个距离有利于Stat5a四聚体结合。这些数据为Stat5a四聚体的形成提供了见解，并表明该转录因子潜在结合位点的范围比预期的更广。
