REGULATION AND FUNCTION OF THE TAL1/SCL GENE

TAL1基因的不适当表达(以前称为SCL和 TCL5)是在T细胞中观察到的最常见的功能获得突变 急性淋巴细胞性白血病。TAL1，基本螺旋环的成员- 螺旋转录因子家族，也已通过基因表现出来 有针对性的研究在ALL的发展中发挥重要作用 造血血统。尽管这些观察表明这种基因 必须调节细胞生长的关键过程，人们对此知之甚少 无论是它的正常行为还是它的错误表达如何导致 白血病的发生。我们已经确定了 哪种TAL1蛋白是在小鼠和鸟类胚胎发育中产生的， 证明Tal1的RNA、蛋白质、DNA结合活性受到调控 通过小鼠红系祖细胞中的促红细胞生成素，定义了几个 Tal1蛋白磷酸化的部位和功能后果 在红系细胞中，并确定Tal1可以与成员合作 与之共表达的另一类T细胞癌蛋白 白血病在改变永生化细胞增殖和存活中的作用 小鼠成纤维细胞。此续订申请概述了一系列 旨在阐明其在造血中的具体作用的实验 生理上表达它的细胞及其作用机制 哪种TAL1改变其所在细胞的增殖和存活 是错误的表达。第一个具体目标是确定TAL1 表达或活性受细胞周期调控。TAL1 将检测丰度、dna结合活性和磷酸化。 在红细胞生成素依赖的红系祖细胞中同步 细胞周期的不同阶段。第二个具体目标是 阐明TAL1在正常生长控制中的作用。一种DNA 结合缺陷的Tal1突变体将在 促红细胞生成素依赖的红系细胞系及其特异性效应 决定了细胞的增殖、存活和分化。第三 具体目的是阐明错误表达的机制 TAL1改变了生长控制。改变生长的基础和 共表达TAL1和另一种T细胞的NIH 3T3细胞的存活 细胞癌蛋白LMO1将被确定，并候选进行调节 或调解这些行为将受到审查。这些研究的结果 将促进对造血分化的基本理解和 提供对白血病发生机制的见解。

Inappropriate expression of the TAL1 gene (formerly known as SCL and TCL5) is the most frequent gain-of-function mutation observed in T-cell acute lymphoblastic leukemia. TAL1, a member of the basic helix-loop- helix family of transcription factors, has also been shown through gene targeting studies to have an essential role in the development of all hematopoietic lineages. Although these observations suggest the gene must regulate critical processes in cell growth, little is known about either its normal actions or how its misexpression contributes to leukemogenesis. We have established the locations and cell types in which TAL1 protein is made in murine and avian embryonic development, demonstrated that Tal1 RNA, protein, DNA-binding activity are regulated by erythropoietin in murine erythroid progenitors, defined several of the sites and functional consequences of Tal1 protein phosphorylation in erythroid cells, and determined that Tal1 can cooperate with members of another class of T-cell oncoproteins with which it is coexpressed in leukemias in altering the proliferation and survival of immortalized mouse fibroblasts. This renewal application outlines a series of experiments aimed at elucidating its specific actions in hematopoietic cells in which it is expressed physiologically and the mechanism by which TAL1 alters the proliferation and survival of cells in which it is misexpressed. The first specific aim is to determine whether TAL1 expression or activity is subject to cell-cycle regulation. Tal1 abundance, DNA-binding activity, and phosphorylation will be examined in erythropoietin-dependent erythroid progenitors synchronized in different phases of the cell cycle. The second specific aim is to elucidate the functions of TAL1 in normal growth control. A DNA binding-defective Tal1 mutant will be inducibly expressed in an erythropoietin-dependent erythroid cell line and its specific effects on proliferation, survival, and differentiation determined. The third specific aim is to elucidate the mechanism by which misexpression of TAL1 alters growth control. The basis for the altered growth and survival of NIH 3T3 cells engineered to coexpress TAL1 with another T- cell oncoprotein, LMO1, will be determined, and candidates to modulate or mediate these actions will be examined. The results of these studies will advance basic understanding of hematopoietic differentiation and provide insights into mechanisms of leukemogenesis.