ACTIVATION OF THE C-MYB PROTO-ONCOGENE

这个项目的总体目标是了解分子机制 c-myb原癌基因通过其调节正常和恶性肿瘤 造血 我们最近的研究表明， c-Myb蛋白不足以转化正常造血细胞 细胞 相反，氨基（N-）或羧基的截短 (C-)c-Myb的末端导致早幼粒细胞的转化 （粒细胞前体），而同时截短的N- 而c-Myb的C-末端导致成髓细胞的转化 （早幼粒细胞前体）。 这两种表型都不同于 由双截短的 禽成髓细胞瘤病毒的v-Myb蛋白，含有11个氨基酸 相对于c-Myb的酸取代。我们还表明， c-Myb的N-或C-末端与v-Myb蛋白的结合抑制了 转型这些结果表明，c- Myb可以作为负调控域。不同形式的能力 c-Myb转化不同类型的细胞也表明， 自身可能参与造血谱系的调控 保持战略定力这一假设得到了最近的证明的支持。 具有c-myb纯合破坏的小鼠在胎儿发育中有缺陷， 造血因此，我们今后五年的具体目标是： 如下所示： (l)为了精确定义N-和C-末端的结构特征， 必须改变c-Myb的表达才能引起转化和改变谱系 保持战略定力 (2)为了确定改变c-末端N-和C-末端的影响， Myb对蛋白质构象、DNA结合和转录调控的影响。 (3)为了确定选择性剪接外显子对 正常和改变形式的c-Myb的功能。 (4)在克隆鸡B中应用高频同源重组技术 细胞系直接检查c-Myb在造血谱系中的作用 保持战略定力 (5)分析转基因小鼠的造血和淋巴分化， 表达各种形式c-Myb的小鼠品系，包括组织- Myb功能的显性抑制剂的特异性表达。

The overall goal of this project is to understand the molecular mechanisms by which the c-myb proto-oncogene regulates normal and malignant hematopoiesis. We have recently shown that constitutive overexpression of the c-Myb protein is not sufficient to transform normal hematopoietic cells. In contrast, truncation of either the amino (N-) or the carboxyl (C-) terminus of c-Myb results in the transformation of promyelocytes (granulocyte precursors), whereas simultaneous truncation of both the N- and C-termini of c-Myb results in the transformation of myeloblasts (promyelocyte precursors). Both of these phenotypes differ from that of the monoblasts (macrophage precursors) transformed by the doubly truncated v-Myb protein of the avian myeloblastosis virus that contains eleven amino acid substitutions relative to c-Myb. We have also shown that the fusion of either the N- or C- terminus of c-Myb to the v-Myb protein suppresses transformation. These results imply that both the N- and C-termini of c- Myb can act as negative regulatory domains. The ability of different forms of c-Myb to transform different types of cells also suggests that c-Myb itself may participate in the control of hematopoietic lineage determination. This hypothesis is supported by the recent demonstration that mice with a homozygous disruption of c-myb are defective in fetal hematopoiesis. Accordingly, our specific aims for the next five years are as follows: (l) To precisely define which structural features of the N- and C-termini of c-Myb must be altered to cause transformation and alter lineage determination. (2) To determine the effects of alterations of the N- and C-termini of c- Myb on protein conformation, DNA-binding, and transcriptional regulation. (3) To determine the effects of alternatively spliced exons on the function of normal and altered forms o c-Myb. (4) To use high frequency homologous recombination in clonal chicken B cell lines to directly examine the role of c-Myb in hematopoietic lineage determination. (5) To analyze hematopoietic and lymphoid differentiation in transgenic lines of mice that express various forms of c-Myb, including the tissue- specific expression of dominant inhibitors of Myb function.