Livingstone C, Patel G, Jones N
Laboratory of Gene Regulation, Imperial Cancer Research Fund, London, UK.
EMBO J. 1995 Apr 18;14(8):1785-97. doi: 10.1002/j.1460-2075.1995.tb07167.x.
The ATF-2 transcription factor can mediate adenovirus E1A-inducible transcriptional activation. Deletion analysis has indicated that the N-terminal region of ATF-2 is essential for this response. Furthermore, the N-terminus can activate transcription in the absence of E1A when fused to a heterologous DNA binding domain. However, in the intact protein this activation domain is masked. In this report we show that residues in the N-terminus required for activation are also required for mediating E1A stimulation. In particular two threonine residues at positions 69 and 71 are essential. These residues are phosphorylated in vivo and can be efficiently phosphorylated in vitro by the JNK/SAPK subgroup of the MAPK family. ATF-2 can bind to a UV-inducible kinase through a region in the N-terminus that is distinct from the sites of phosphorylation; this binding region is both necessary for phosphorylation by JNK/SAPK in vitro and for transcriptional activation in vivo. The activity of the N-terminus is stimulated by UV irradiation which stimulates the signalling pathway leading to JNK/SAPK. Finally, although ATF-2 binds to the E1A protein, the N-terminal activation domain is not required for this interaction. The results show that ATF-2, like other members of the ATF/CREB family of DNA binding proteins is regulated by specific signalling pathways.
ATF-2转录因子可介导腺病毒E1A诱导的转录激活。缺失分析表明，ATF-2的N端区域对于这种反应至关重要。此外，当与异源DNA结合结构域融合时，N端在没有E1A的情况下也能激活转录。然而，在完整蛋白中，这个激活结构域被掩盖了。在本报告中，我们表明激活所需的N端残基对于介导E1A刺激也是必需的。特别是第69和71位的两个苏氨酸残基至关重要。这些残基在体内被磷酸化，并且在体外可以被MAPK家族的JNK/SAPK亚组有效磷酸化。ATF-2可以通过N端一个不同于磷酸化位点的区域与紫外线诱导激酶结合；这个结合区域对于体外JNK/SAPK磷酸化和体内转录激活都是必需的。N端的活性受到紫外线照射的刺激，紫外线照射刺激导致JNK/SAPK的信号通路。最后，尽管ATF-2与E1A蛋白结合，但这种相互作用不需要N端激活结构域。结果表明，ATF-2与DNA结合蛋白ATF/CREB家族的其他成员一样，受特定信号通路调控。
