The leukemic fusion gene AML1-MDS1-EVI1 suppresses CEBPA in acute myeloid leukemia by activation of Calreticulin
The leukemic fusion gene AML1-MDS1-EVI1 suppresses CEBPA in acute myeloid leukemia by activation of Calreticulin
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DOI：
10.1073/pnas.0404731101
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发表时间：
2004-09-07
影响因子：
11.1
通讯作者：
Pabst, T
中科院分区：
文献类型：
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作者：
Helbling, D;Mueller, BU;Pabst, T
白血病融合基因AML 1-MDS 1-EVI 1（AME）编码一种嵌合转录因子，该因子由急性髓性白血病、治疗相关骨髓增生异常综合征或慢性髓性白血病急变期患者中观察到的t（3，21）（q26;q22）易位引起。髓系转录因子CEBPA对正常粒细胞生成至关重要。在这里，我们发现条件表达的AME抑制CEBPA蛋白90.8%和DNA结合活性93.9%。相反，CEBPA mRNA水平保持不变。此外，我们检测到携带AME易位的患者（n = 8）的白血病原始细胞中CEBPA mRNA水平与具有正常核型的急性髓性白血病患者（n = 9）相比没有差异。然而，CEBPA蛋白和结合活性在AME患者样品中显著降低（分别为100%和92.1%）。此外，我们观察到，钙网蛋白（CRT），一个假定的抑制剂CEBPA翻译，强烈激活后，诱导AME在细胞系系统（14.8倍）和AME患者样本（12.2倍）。此外，通过小干扰RNA抑制CRT有力地恢复CEBPA水平。这些结果确定CEBPA作为白血病融合蛋白AME的一个关键目标，并表明CRT对CEBPA的调节可能是AME白血病分化阻滞的一种机制。
The leukemic fusion gene AML1-MDS1-EVI1 (AME) encodes a chimeric transcription factor that results from the t(3,21)(q26;q22) translocation seen in patients with acute myeloid leukemia, with therapy-related myelodysplastic syndrome, or with chronic myeloid leukemia in blast crisis. The myeloid transcription factor CEBPA is crucial for normal granulopoiesis. Here, we found that conditional expression of AME suppresses CEBPA protein by 90.8% and DNA-binding activity by 93.9%. In contrast, CEBPA mRNA levels remained unchanged. In addition, we detected no differences in CEBPA mRNA levels in leukemic blasts of patients carrying the AME translocation (n = 8) compared to acute myeloid leukemia patients with a normal karyotype (n = 9). CEBPA protein and binding activity, however, were reduced significantly (100% and 92.1%, respectively) in AME patient samples. Furthermore, we observed that calreticulin (CRT), a putative inhibitor of CEBPA translation, was strongly activated after induction of AME in the cell-line system (14.8-fold) and in AME patient samples (12.2-fold). Moreover, inhibition of CRT by small interfering RNA powerfully restored CEBPA levels. These results identify CEBPA as a key target of the leukemic fusion protein AME and suggest that modulation of CEBPA by CRT may represent a mechanism involved in the differentiation block in AME leukemias.