Ishida S, Yoshida K, Kaneko Y, Tanaka Y, Sasaki Y, Urano F, Umezawa A, Hata J, Fujinaga K
Department of Molecular Biology, Cancer Research Institute, School of Medicine, Sapporo Medical University, Sapporo (Japan).
Cytogenet Cell Genet. 1998;82(3-4):278-83. doi: 10.1159/000015119.
Chromosome translocation creates a fusion between the EWSR1 gene and an ETS family gene. The fusion between these two genes is a characteristic feature of Ewing sarcoma. We previously identified a fourth translocation, t(17;22)(q12;q12), in genomic DNA isolated from cells of patients affected with Ewing sarcoma. The discovery of this translocation suggested that there might be a novel EWSR1-ETV4 fusion gene. In the present study, we determined the genomic breakpoint and characterized the chimeric transcript of the EWSR1-ETV4 fusion gene in two t(17;22) Ewing sarcomas. Reverse transcriptase-PCR assay showed an in-frame fusion between the 5'-terminal region of EWSR1 and the 3' end of ETV4 (alias E1AF, PEA3); the chimeric transcript could thus serve as a template for expression of a protein composed of the N-terminal portion of EWSR1 fused to the DNA-binding domain of ETV4. Long PCR and sequence analysis of genomic DNA revealed that either exon 8 or intron 7 of EWSR1 is fused to the same intron of ETV4 in both tumors. Several palindromic oligomer sequences were found close to the breakpoints in both genes. The 159-bp Alu-like sequence was repeated in the breakpoint region of the ETV4 gene. These observations suggest a mechanism of EWSR1-ETV4 gene fusion.
染色体易位导致EWSR1基因与ETS家族基因发生融合。这两个基因的融合是尤因肉瘤的一个特征性表现。我们之前在从尤因肉瘤患者细胞中分离出的基因组DNA中鉴定出了第四种易位，即t(17;22)(q12;q12)。这种易位的发现提示可能存在一种新的EWSR1 - ETV4融合基因。在本研究中，我们确定了两个t(17;22)尤因肉瘤中EWSR1 - ETV4融合基因的基因组断点，并对其嵌合转录本进行了特征分析。逆转录酶 - PCR分析显示EWSR1的5'端区域与ETV4（别名E1AF、PEA3）的3'端发生了读框内融合；因此，嵌合转录本可作为一种蛋白质表达的模板，该蛋白质由EWSR1的N端部分与ETV4的DNA结合结构域融合而成。基因组DNA的长PCR和序列分析表明，在这两个肿瘤中，EWSR1的外显子8或内含子7与ETV4的同一个内含子发生了融合。在两个基因的断点附近发现了几个回文寡聚体序列。159bp的类Alu序列在ETV4基因的断点区域重复出现。这些观察结果提示了EWSR1 - ETV4基因融合的机制。
