Abstract：
HOXA9 transcription factor is expressed in hematopoietic stem cells and is involved in the regulation of their differentiation and maturation to various blood cells. HOXA9 is linked to various leukemia and is a marker for poor prognosis of acute myeloid leukemia (AML). This protein has a conserved DNA-binding homeodomain and a transactivation domain. We show that this N-terminal transactivation domain is intrinsically disordered and inhibits DNA-binding by the homeodomain. Using NMR spectroscopy and molecular dynamics simulation, we show that the hexapeptide 197AANWLH202 in the disordered region transiently occludes the DNA-binding interface. The hexapeptide also forms a rigid segment, as determined by NMR dynamics, in an otherwise flexible disordered region. Interestingly, this hexapeptide is known to mediate the interaction of HOXA9 and its TALE partner proteins, such as PBX1, and help in cooperative DNA binding. Mutation of tryptophan to alanine in the hexapeptide abrogates the DNA-binding auto-inhibition. We propose that the disordered transactivation region plays a dual role in the regulation of HOXA9 function. In the absence of TALE partners, it inhibits DNA binding, and in the presence of TALE partners it interacts with the TALE protein and facilitates the cooperative DNA binding by the HOX-TALE complex.
摘要：
HOXA9转录因子在造血干细胞中表达，并参与其分化和成熟为各种血细胞的调节。HOXA9与各种白血病有关，是急性髓性白血病（AML）预后不良的标志物。该蛋白质具有保守的DNA结合同源结构域和反式激活结构域。我们表明，该N末端反式激活域本质上是无序的，并抑制同源域的DNA结合。利用核磁共振波谱和分子动力学模拟,我们显示，无序区域的六肽197AANWLH202暂时封闭了DNA结合界面。六肽也形成刚性片段，由核磁共振动力学确定，在一个灵活的无序区域。有趣的是,已知这种六肽介导HOXA9与其TALE伴侣蛋白的相互作用，如PBX1，并有助于协同DNA结合。六肽中色氨酸向丙氨酸的突变消除了DNA结合自抑制。我们建议无序的反式激活区在HOXA9功能的调节中起着双重作用。在没有TALE合作伙伴的情况下，它抑制DNA结合，并且在TALE伴侣的存在下，它与TALE蛋白相互作用，并促进HOX-TALE复合物的协同DNA结合。
