Lessnick S L, Braun B S, Denny C T, May W A
Molecular Biology Institute, Gwynne Hazen Cherry Memorial Laboratories, University of California, Los Angeles 90024.
Oncogene. 1995 Feb 2;10(3):423-31.
The (11;22) chromosomal translocation found in Ewing's sarcoma and related tumors fuses the amino terminus of the EWS protein to the DNA-binding domain of the FLI-1 transcription factor. In contrast to normal FLI-1, the EWS/FLI-1 fusion transforms NIH3T3 cells and this activity requires both EWS and FLI-1 sequences. Reporter gene assays showed that the portion of EWS fused to FLI-1 encodes a strong transcriptional activation domain. To determine whether this function is necessary for transformation by EWS/FLI-1, deletion analysis of EWS was performed. We found that the EWS domain could be functionally subdivided into two regions: (i) an amino terminal domain (domain A) which transforms efficiently when fused to FLI-1 but has little transactivation activity in a model system and (ii) a distal region (domain B) which transactivates efficiently but transforms less efficiently when fused to FLI-1. Replacement of the EWS domain with known heterologous transcriptional activation domains yielded chimeric FLI-1 fusions that in some instances could transform NIH3T3 cells. Finally we demonstrate that EWS/FLI-1 and related FLI-1 chimeras are able to cooperate with another transcription factor to activate a model reporter gene. These results further demonstrate that EWS/FLI-1 is an aberrant transcription factor and suggest that the EWS domain mediates important protein-protein interactions with other factors resulting in the transcriptional modulation of target genes.
在尤因肉瘤及相关肿瘤中发现的（11；22）染色体易位，将EWS蛋白的氨基末端与FLI-1转录因子的DNA结合结构域融合。与正常的FLI-1不同，EWS/FLI-1融合体可转化NIH3T3细胞，且这种活性需要EWS和FLI-1序列。报告基因检测表明，与FLI-1融合的EWS部分编码一个强大的转录激活结构域。为确定该功能对于EWS/FLI-1介导的转化是否必要，对EWS进行了缺失分析。我们发现EWS结构域在功能上可细分为两个区域：（i）氨基末端结构域（结构域A），当与FLI-1融合时能高效转化，但在模型系统中几乎没有反式激活活性；（ii）远端区域（结构域B），能高效反式激活，但与FLI-1融合时转化效率较低。用已知的异源转录激活结构域替换EWS结构域，产生了嵌合的FLI-1融合体，在某些情况下可转化NIH3T3细胞。最后，我们证明EWS/FLI-1及相关的FLI-1嵌合体能够与另一种转录因子协同激活一个模型报告基因。这些结果进一步证明EWS/FLI-1是一种异常转录因子，并表明EWS结构域介导了与其他因子的重要蛋白质-蛋白质相互作用，从而导致靶基因的转录调控。
