CHIMERIC E2A-HLF TRANSCRIPTION FACTORS IN ACUTE LEUKEMIA

编码转录因子的基因是特异性转录因子的靶点。 染色体易位在人类白血病细胞，但机制， 它们促进的异常生长和分化仍然在很大程度上 未定义。 这项建议的重点是肝白血病因子（HLF）， 新鉴定的序列特异性DNA结合蛋白 碱性区/亮氨酸拉链（bZip）超家族。 A t（17;19）（q22;pl3） 儿童B系急性淋巴细胞染色体易位 白血病（ALL）在17号染色体上的断点处破坏HLF基因 和19号染色体上断点处的E2 A基因。所得融合 基因（E2 A-HLF）产生嵌合蛋白，保留氨基末端 E2 A的转录激活结构域，但不是其基本的 螺旋-环-螺旋结构域，其被bZip DNA结合取代， HLF蛋白的二聚化结构域。 一个有吸引力的假设， 解释了早期E2 A-HLF基因重排的情况 B系ALL是嵌合蛋白导致恶性 转化并确保维持白血病状态。 的 拟议的研究将在两个不同但互补的领域进行， HLF和E2 A-HLF蛋白在糖尿病发病机制中的作用 儿童急性白血病 首先，E2 A-HLF和HLF蛋白的能力 为了调节构建体中报告基因的表达，所述构建体含有 将检测介导HLF结合的顺式作用DNA序列， 淋巴样和髓样白血病细胞系。 这些研究还将评估 HLF与其他bZip蛋白异二聚化的能力， 为了确定正常或嵌合HLF的同源或异源二聚体 蛋白激活白血病细胞中关键靶基因的表达 细胞 同时，祖细胞的致癌潜力和谱 对这些蛋白质的转化作用敏感的细胞将被 在用逆转录病毒载体感染的鼠骨髓细胞中测定 携带E2 A-HLF或HLF cDNA。 嵌合E2 A-HLF的功能结构域 蛋白质将分别进行测试，以确定这种杂交蛋白质 可以破坏通常控制生长的转录程序 和造血细胞的分化。 更好地了解 这些转录因子与人类急性白血病的关系 应该会产生关于调节电路的重要信息 控制正常的造血，并可能提出新的方法， 造血系统恶性肿瘤的诊断和治疗。

Genes encoding transcription factors are the targets of specific chromosomal translocations in human leukemic cells, but the mechanisms by which they promote aberrant growth and differentiation are still largely undefined. This proposal focuses on hepatic leukemia factor (HLF), a newly identified sequence-specific DNA-binding protein of the basic-region/leucine-zipper (bZip) superfamily. A t(17;19)(q22;pl3) chromosomal translocation in childhood B-lineage acute lymphoblastic leukemia (ALL) disrupts the HLF gene at the breakpoint on chromosome 17 and the E2A gene at the breakpoint on chromosome 19. The resulting fusion gene (E2A-HLF) produces chimeric proteins that retain the amino-terminal transcriptional activation domain of E2A, but not its basic helix-loop-helix domain, which is replaced by the bZip DNA-binding and dimerization domain of the HLF protein. An attractive hypothesis to account for productive E2A-HLF gene rearrangements in cases of early B-lineage ALL is that the chimeric proteins contribute to malignant transformation and ensure maintenance of the leukemic state. The proposed research will be conducted on two distinct but complementary aspects of the roles of HLF and E2A-HLF proteins in the pathogenesis of childhood acute leukemia. First, the ability of E2A-HLF and HLF proteins to regulate the expression of reporter genes in constructs containing cis-acting DNA sequences that mediate HLF binding will be tested in lymphoid and myeloid leukemia cell lines. These studies will also assess the ability of HLF to heterodimerize with other bZip proteins, in order to determine whether homo- or heterodimers of normal or chimeric HLF proteins activate the expression of critical target genes in leukemic cells. Concurrently, the oncogenic potential and spectrum of progenitor cells susceptible to the transforming effects of these proteins will be determined in murine bone marrow cells infected with retroviral vectors carrying E2A-HLF or HLF cDNAs. Functional domains of chimeric E2A-HLF proteins will be tested separately, to determine how this hybrid protein can subvert the transcriptional programs that normally control the growth and differentiation of hematopoietic cells. Improved understanding of the involvement of these transcription factors in human acute leukemias should yield important information about the regulatory circuits governing normal hematopoiesis and may suggest new approaches for the diagnosis and treatment of hematopoietic malignancies.