Pan S, Ming K Y, Dunn T A, Li K K, Lee K A
Department of Biology, Hong Kong University of Science & Technology, Kowloon, PRC.
Oncogene. 1998 Mar 26;16(12):1625-31. doi: 10.1038/sj.onc.1201671.
Naturally occurring chromosomal fusion of the Ewings Sarcoma Oncogene (EWS) to distinct cellular transcription factors, produces aberrant transcriptional activators that function as dominant oncogenes. In Malignant Melanoma of Soft Parts the N-terminal region of EWS is fused to C-terminal region of the cAMP-inducible transcription factor ATF1. The EWS/ATF1 fusion protein binds to ATF sites present in cAMP-responsive promoters via the ATF1 bZIP domain and activates transcription constitutively in a manner that is dependent on an activation domain (EAD) present in EWS. To further define the requirements for trans-activation we have performed mutational analysis of EWS/ATF1 in mammalian cells and report several new findings. First, trans-activation by EWS/ATF1 does not require dimerisation with other ATF family members present in mammalian cells. Second, in contrast to the earlier suggestion of an allosteric role, the EAD can act directly. Third, determinants of trans-activation are dispersed throughout the EAD and cooperate synergistically to produce potent trans-activation. We also report that the region of EWS containing the EAD can activate transcription in Yeast. This latter finding might enable a genetic approach to understanding the mechanism of transcriptional activation by EWS and development of high-throughput screens for EWS inhibitors.
尤因肉瘤癌基因（EWS）与不同的细胞转录因子发生自然发生的染色体融合，产生异常的转录激活因子，这些因子作为显性癌基因发挥作用。在软组织恶性黑色素瘤中，EWS的N端区域与cAMP诱导转录因子ATF1的C端区域融合。EWS/ATF1融合蛋白通过ATF1的bZIP结构域与cAMP反应性启动子中存在的ATF位点结合，并以依赖于EWS中存在的激活结构域（EAD）的方式组成性地激活转录。为了进一步确定反式激活的要求，我们在哺乳动物细胞中对EWS/ATF1进行了突变分析，并报告了几个新发现。首先，EWS/ATF1的反式激活不需要与哺乳动物细胞中存在的其他ATF家族成员二聚化。其次，与早期关于变构作用的建议相反，EAD可以直接发挥作用。第三，反式激活的决定因素分散在整个EAD中，并协同作用以产生有效的反式激活。我们还报告说，包含EAD的EWS区域可以在酵母中激活转录。后一个发现可能使我们能够采用遗传学方法来理解EWS转录激活的机制，并开发针对EWS抑制剂的高通量筛选方法。
