Yamamoto K, Seto M, Komatsu H, Iida S, Akao Y, Kojima S, Kodera Y, Nakazawa S, Ariyoshi Y, Takahashi T
Laboratories of Chemotherapy, Aichi Cancer Center Research Institute, Nagoya, Japan.
Oncogene. 1993 Oct;8(10):2617-25.
We previously isolated cDNA clones, MLL-a and MLL-b, derived from the 11q23 breakpoint region and detected gene rearrangements with MLL-b cDNA in infantile leukemia cell lines with 11q23 abnormalities. We also showed chimeric mRNAs between MLL and genes on partner chromosomes such as 4q21 and 19p13. In the present study, we isolated overlapping MLL cDNA clones of 11 kb and demonstrated that MLL-a and MLL-b were derived from the same gene, MLL/ALL-1/HRX. Northern analysis with an MLL cDNA probe detected different signals in t(11;19) cell lines, one being sized 10 kb in two cell lines, KOCL-33 and KOCL-44, and the other being 9.2 kb in the cell line, KOPN-1. To elucidate the molecular basis for the heterogeneity, we isolated cDNA clones of a translocation-associated gene on chromosome 19, LTG19, as well as chimeric cDNAs from KOPN-1. Northern analysis with LTG19 cDNA demonstrated the identical gene, encoding serine/proline rich 559 amino acid polypeptide, to be involved in all three cell lines. Sequence comparison revealed that the LTG19 portion of the predicted chimeric protein of KOPN-1 was fused in frame and contained the C-terminal 189 amino acids. This was shorter by 366 amino acids than those of KOCL-33 and KOCL-44, also fused in frame. Reverse transcriptase-PCR analysis demonstrated complex chimeric mRNAs in cell lines and leukemia samples. Although a chimeric mRNA of KOPN-1 type was rare, its presence suggested that the shared C-terminal portion of 189 amino acids of LTG19 contains important signal(s) for malignant transformation.
我们之前从11q23断点区域分离出了cDNA克隆MLL-a和MLL-b，并在具有11q23异常的婴儿白血病细胞系中检测到了与MLL-b cDNA的基因重排。我们还展示了MLL与伙伴染色体（如4q21和19p13）上的基因之间的嵌合mRNA。在本研究中，我们分离出了11 kb的重叠MLL cDNA克隆，并证明MLL-a和MLL-b源自同一基因MLL/ALL-1/HRX。用MLL cDNA探针进行的Northern分析在t(11;19)细胞系中检测到了不同的信号，其中一个在KOCL-33和KOCL-44这两个细胞系中的大小为10 kb，另一个在KOPN-1细胞系中的大小为9.2 kb。为了阐明这种异质性的分子基础，我们分离出了19号染色体上一个易位相关基因LTG19的cDNA克隆，以及来自KOPN-1的嵌合cDNA。用LTG19 cDNA进行的Northern分析表明，同一个编码富含丝氨酸/脯氨酸的559个氨基酸多肽的基因参与了所有三个细胞系。序列比较显示，KOPN-1预测嵌合蛋白的LTG19部分是框内融合的，包含C端的189个氨基酸。这比同样框内融合的KOCL-33和KOCL-44的氨基酸短366个。逆转录酶-PCR分析在细胞系和白血病样本中显示出复杂的嵌合mRNA。尽管KOPN-1型的嵌合mRNA很少见，但其存在表明LTG19共有的189个氨基酸的C端部分含有恶性转化的重要信号。
