CHIMERIC E2A-HLF TRANSCRIPTION FACTORS IN ACUTE LEUKEMIA

编码转录因子的基因是特异性的靶标 人类白血病细胞中的染色体易位，但其机制是 它们促进的异常生长和分化在很大程度上仍然 未定义。这项建议的重点是肝白血病因子(HLF)，一种 新发现的序列特异性DNA结合蛋白 基本区域/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号染色体的断裂点破坏HLF基因 以及位于19号染色体断裂点的E2A基因。由此产生的融合 基因(E2A-HLF)产生保留氨基末端的嵌合蛋白 E2a转录激活结构域，但不是其基本结构域 螺旋-环-螺旋结构域，被bZip DNA结合和 HLF蛋白的二聚化结构域。一个吸引人的假设 早期E2A-HLF基因重排的原因 B系ALL是嵌合蛋白致癌的原因 转变，确保白血病状态的维持。这个 拟议的研究将在两个截然不同但相辅相成的 HLF和E2A-HLF蛋白在卵巢癌发病机制中的作用 儿童急性白血病。第一，E2A-HLF和HLF蛋白的能力 为了调节报告基因在包含以下内容的构建体中的表达 介导HLF结合的顺式作用DNA序列将在 淋巴细胞系和髓系白血病细胞系。这些研究还将评估 HLF与其他bZip蛋白异源二聚体的能力 确定正常或嵌合HLF的同源或异源二聚体 蛋白质激活白血病关键靶基因的表达 细胞。同时，前体细胞的致癌潜能和致癌谱 易受这些蛋白质转化影响的细胞将是 在感染逆转录病毒载体的小鼠骨髓细胞中检测到 携带E2A-HLF或HLF cDNA。嵌合E2A-HLF的功能结构域 蛋白质将被单独测试，以确定这种杂交蛋白质如何 可以颠覆正常控制生长的转录程序 和造血细胞的分化。更好地理解 这些转录因子在人类急性白血病中的作用 应提供有关调节电路的重要信息 管理正常的造血，并可能提出新的方法 血液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.