Development and clinical application of molecular diagnosis in leukemias

t（3 ; 21）（q26 ; q22）易位是慢性粒细胞白血病（CML）急变期常见的染色体异常之一，被认为在CML向急性急变期的进展中起重要作用。AML 1基因位于急性髓细胞白血病中发现的t（8 ; 21）（q22 ; q22）易位的易位断裂点，也被t（3 ; 21）（q26 ; q22）易位重排。筛选携带t（3 ; 21）的白血病细胞系细胞（SKH 1）的cDNA文库导致分离AML 1/EVI-1嵌合cDNA。SKH 1细胞表达180 kD的AML 1/EVI-1融合蛋白，其含有AML 1的氨基末端的一半，包括与整个锌指EVI-1蛋白融合的runt同源结构域。这些发现有力地表明t（3 ; 21）易位导致一类新的嵌合转录因子的形成，这类转录因子可能有助于CML的白血病进展。 ...更多信息 充分干扰细胞生长和分化。生化分析显示，AML 1/EVI-1本身不改变通过PEBP 2位点的反式激活水平，但主要抑制由完整的AML 1，这被认为是一个刺激剂的髓样细胞分化的反式激活。AML 1/EVI-1与PEBP 2位点的结合亲和力高于AML 1，DNA结合竞争是AML 1/EVI-1显性负效应的可能机制。AML 1/EVI-1还可激活c-fos启动子的反式激活，提高AP-1活性。使用AML 1/EVI-1缺失突变体的实验表明，这两种功能是相互独立的，因为对完整AML 1的显性负效应和AP-1活性的刺激分别依赖于C末端附近的runt结构域和锌指结构域。此外，我们发现，AML 1/EVI-1块粒细胞分化，否则诱导的G-CSF，32 Dc 13髓样细胞。还表明融合蛋白的AML 1衍生部分和EVI-1衍生部分在这种分化阻断中起关键作用。结论：t（3 ; 21）白血病的白血病细胞转化可能是由AML 1/EVI-1嵌合蛋白的双重功能引起的。少

The t (3 ; 21) (q26 ; q22)translocation, which is one of consistent chromosomal abnormalities found in blastic crisis of chronic myelocytic leukemia(CML) , is thought to play an important role in leukemic progression of CML to an acute blastic crisis phase. The AML1 gene, which is located at the translocation breakpoint of the t (8 ; 21) (q22 ; q22) translocation found in acute myelocytic leukemia, was also rearranged by the t (3 ; 21) (q26 ; q22) translocation. Screening of a cDNA library of the t (3 ; 21) -carrying leukemic cell line cells (SKH1) resulted in the isolation of AML1/EVI-1 chimeric cDNAs. SKH1 cells expressed the 180 kD AML1/EVI-1 fusion protein containing an amino-terminal half of AML1 including a runt homology domain which is fused to the entire of zinc finger EVI-1 protein. These findings strogly suggest that the t (3 ; 21) translocation results in the fromation of a new class of a chimeric transcription factor which could contribute to leukemic progression of CML thr … More ough interference with cell growth and differentiation. Biochemical analyzes revealed that AML1/EVI-1 itself does not alter the transactivation level through PEBP2 sites but dominantly suppresses the transactivation by intact AML1, which is assumed to be a stimulator of myeloid cell differentiation. The DNA-binding competition is a putative mechanism of such dominant negative effects of AML1/EVI-1 because it binds to PEBP2 sites in the higher affinity than AML1.Furthermore, AML1/EVI-1 stimulated the c-fos promoter transactivation and raised the AP-1 activity. Experiments, using deletion mutants of AML1/EVI-1, showed that these two functions are mutually independent because the dominant negative effects upon intact AML1 and the stimulation of AP-1 activity are dependent on the runt domain and the zinc finger domain near the C-terminus, respectively. Furthermore we showed that AML1/EVI-1 blocks granulocytic differentiation, otherwise induced by G-CSF,of 32Dc13 myeloid cells. It was also suggested that both AML1-derived and EVI-1-derived portions of the fusion protein play crucial roles for such differentiation block. We conclude that the leukemic cell transformation in t (3 ; 21) leukemias is probably caused by those dual functions of AML1/EVI-1 chimeric protein. Less