Study on the induction mechanism of exon skipping and tumorigenesis by 12-repeats

我们在牛T淋巴瘤细胞系BTL-26的c-myb基因外显子9中发现了一个串联重复的12核苷酸基序（TGATCTGCCCGT）。我们研究了牛散发性淋巴肉瘤的其他T淋巴瘤细胞系中12-重复基序的存在情况、12-重复基序诱导c-myb基因外显子9跳跃的机制以及牛T淋巴瘤的发生与c-Myb蛋白高转录激活活性的关系.在包括BTL-26在内的三个T淋巴瘤细胞系（pr 1818和Pr 2410）的c-myb基因外显子9中发现了12个核苷酸基序的插入。除了12-重复序列外，在每个细胞系中还观察到不同的9-核苷酸基序（TCTGGGCGT）。重复单位数为4 ~ 17份.为了了解DNA环修复的缺陷是否涉及重复序列的不稳定性，检查了结合和纠正核提取物中环结构的能力。提示牛T淋巴瘤细胞中12-重复序列的不稳定性可能与DNA环修复功能缺陷无关. 12重复序列含有c-Myb的结合位点（CAACG），在表达c-Myb或v-Myb的细胞中具有反式激活报告基因的能力。从微基因质粒分析结果来看，c-myb基因外显子9的缺失是由12-重复序列的插入引起的，而不是12-重复序列与c-Myb之间的相互作用. c-Myb外显子9跳读与牛T淋巴瘤发生的密切关系尚未得到解决。

We found a tandemly repeated 12-nucleotide motif (TGATCTGCCCGT) inserted into the c-myb gene exon 9 in a bovine T-lymphoma cell line BTL-26 which has been established from a calf type of bovine sporadic lymphosarcomas. We investigated the presence of 12-repeat motifs in the other T-lymphoma cell lines from bovine sporadic lymphosarcomas, induction mechanisms of exon 9 skipping in c-myb gene by the 12-repeat motifs and any relationship of turnorigenesis of bovine T-lymphoma and high-transcription-activating activity of c-Myb protein.1. Insertion of a 12-nucleotide motif was found in the c-myb gene exon 9 from three T-lymphoma cell lines (pr1818 and Pr2410) including BTL-26. In addition to 12-repeat, the different 9-nucletide motifs (TCTGGGCGT) was also observed in each cell line. The number of retitive unit ranged from 4 to 17 copies.2. To know whether deficiency in DNA loop repair is involved in the instability of the repeat, abilities to bind and correct the loop structure in nuclear extracts were examined. The data suggest that instability of the 12-repeat in bovine T-lymphoma cells might be independent of deficiency of DNA loop repair function.3. The 12-repeat contained the binding sites (CAACG) for c-Myb and had the ability to transactivate reporter gene in the cells expressing c-Myb or v-Myb.4. It appeared that the deletion of c-myb gene exon 9 was induced by the insertion of the the 12-repeat rather than by the interaction between 12-repeat and c-Myb from the mini-gene plasmid analyses.5. The close relationship between the c-Myb exon 9 skipping and tumorigensesis of bovine T-lymphoma remains unsolved in this study.