ANALYSIS OF MULTIPLE CHIMERIC TRANSCRIPTS IN THE T(3;21)

反复发生的染色体易位(3；21)(q26；q22)与初治或治疗相关的急、慢性髓系白血病有关。这种易位是不寻常的，因为它导致了三种不同的融合基因。每个融合基因的作用尚不清楚。其中一个是AML1/MDS1/EVI1，是易位后两个转录激活子的框内连接的结果。它们分别是位于染色体带21q22的胎肝造血所必需的AML1和位于染色体带3q26的MDS1/EVI1。MDS1/EVI1在造血组织中未检测到，但在分化中的造血干细胞中瞬时表达。与转录激活剂AML1和MDS1/EVI1不同，AML1/MDS1/EVI1是一种抑制因子，可以抑制AML1和MDS1/EVI1激活的启动子。本研究的目的是分析AML1/MDS1/EVI1融合蛋白改变导致白血病的造血分化进程的分子机制。我们已经建立了几个模型，表明在造血祖细胞中，AML1/MDS1/EVI1抑制了对控制细胞复制和分化的因素的反应。根据初步结果，我们假设融合蛋白在造血过程中通过扰乱AML1和MDS1/EVI1调控基因的正常调控而发挥作用，导致对造血分化和复制至关重要的谱系特异性因子的表达水平不适当。这项提案涉及的问题是：抑制是如何介导的，融合蛋白的靶标是什么？通过结合生化和分子技术，以及组织培养研究，我们将鉴定AML1/MDS1/EVI1调控的靶蛋白，并评估它们在细胞转化中的作用。我们获得的信息将有助于设计髓系白血病和t(3；21)患者的新治疗方法。此外，我们的结果将为白血病的研究提供洞察力，在这些白血病中，AML 1或MDS1/EVI1被重排。

The recurring chromosomal translocation (3;21)(q26;q22) has been associated with de novo or therapy related acute and chronic myeloid leukemias. This translocation is unusual in that it results in three different fusion genes. The role of each fusion gene is not known. One of them, AML1/MDS1/EVI1, results from the in-frame joining of two transcription activators following the translocation. They are AML1, which is necessary to fetal liver hematopoiesis and is located at chromosome band 21q22, and MDS1/EVI1, located at chromosome band 3q26. MDS1/EVI1 is not detected in hematopoietic tissues, but is transiently expressed in differentiating hematopoietic stem cells. In contrast to AML1 and MDS1/EVI1, which are very strong transcription activators, AML1/MDS1/EVI1 is a repressor, and can inhibit promoters activated by AML1 and MDS1/EVI1. The objective of this proposal is to dissect the molecular mechanisms by which the fusion protein AML1/MDS1/EVI1 alters the progress of the hematopoietic differentiation leading to leukemia. We have developed several models showing that, in hematopoietic precursor cells, AML1/MDS1/EVI1 inhibits the response to factors that control cell replication and differentiation. Based on preliminary results, we hypothesize that the fusion protein acts by disrupting the normal regulation of genes regulated by AML1 and MDS1/EVI1 during hematopoiesis, resulting in inappropriate level of expression of lineage- specific factors critical for hematopoietic differentiation and replication. The questions addressed in this proposal are: How is the repression mediated, and what are the targets of the fusion protein? By using a combination of biochemical and molecular techniques, and tissue culture studies, we will identify the target proteins regulated by AML1/MDS1/EVI1 and assess their role in cell transformation. The information we obtain will be useful in the design of new treatments for patients with myeloid leukemia and a t(3;21). In addition, our results will provide insight in the study of leukemias in which either AML 1 or MDS1/EVI1 are rearranged.