Control of T Lymphopoiesis and Growth by Mad Genes

描述（由申请人提供）：抗原活化淋巴细胞，或白血病转化淋巴细胞，在它们分裂成大小相等的子细胞之前，必须将其大小和内容加倍（称为细胞生长）。尽管细胞生长在正常细胞增殖和癌症中具有重要意义，但在淋巴细胞或其他哺乳动物细胞分裂过程中控制细胞生长的分子事件仍然是一个谜。我们在小鼠中的初步研究表明，Mad家族的基本螺旋-环-螺旋转录因子（Mad1, Mxi1, Mad3, Mad4）被认为是Myc癌蛋白的拮抗剂，部分通过抑制细胞生长来抑制T细胞的增殖和发育。此外，人类mad1和mxi1基因各自定位于与淋巴细胞白血病、霍奇金病和前列腺癌相关的单独染色体区域，这表明mad基因在淋巴细胞生物学和癌症中的重要性。本研究的主要目的是确定Mad家族成员在T淋巴细胞发育和扩增中的正常作用和作用机制。具体而言，我们打算：(1)验证Mad家族成员调节T淋巴细胞成熟的假设。我们将通过在小鼠中使用靶向删除和转基因过表达选定的Mad家族成员来研究Mad家族成员在T淋巴细胞发育中的作用。(2)验证在T细胞活化过程中，Mad家族成员控制T淋巴细胞的增殖和细胞生长（细胞大小、蛋白质合成）的假设。我们将研究Mad过表达或缺失对细胞分裂、细胞大小、RNA加工和原代淋巴细胞在激活后立即合成的功能后果。(3)验证Mad直接结合并调节参与细胞生长控制的必需基因表达的假说。我们将确定Mad1是否抑制参与细胞生长控制的几个必需基因的表达。然后，我们将使用染色质免疫沉淀法来确定这些基因的调控区域是否直接与Mad蛋白结合。总之，这些目标将测试Mad-Max复合物通过控制生长调节基因的表达来正常调节淋巴细胞增殖和发育的整体假设。这些研究的结果将确定可以调节Myc和Mad之间平衡的靶基因，以抑制淋巴瘤或自身免疫性疾病中的淋巴细胞增殖，或在原发性免疫反应中增强抗原特异性淋巴细胞的克隆扩增，或在骨髓移植后。

DESCRIPTION (provided by applicant): Antigen-activated lymphocytes, or transformed lymphocytes in leukemias, must double their size and contents (termed cell growth) before they can divide into equal sized daughter cells. Despite the importance of cell growth in normal cell proliferation and cancer, the molecular events that control cell growth in dividing lymphocytes or other mammalian cells remain an enigma. Our preliminary studies in mice suggest that the Mad family of basic helix-loop-helix transcription factors (Mad1, Mxi1, Mad3, Mad4), considered to be antagonists of the Myc oncoprotein, inhibit T cell proliferation and development in part by inhibiting cell growth. Furthermore, human mad1 and mxi1 genes each localize to separate chromosome regions associated with lymphocytic leukemias, Hodgkin's disease, and prostatic carcinomas suggesting the importance of mad genes in lymphocyte biology and cancer. The broad objective of this proposal is to determine the normal roles and mechanism of action of Mad family members in the development and expansion of T Iymphocytes Specifically, we intend to: (1) Test the hypothesis that Mad family members modulate the maturation of T lymphocytes. We will examine the role(s) of Mad family members in T lymphocyte development by employing targeted deletion, and transgenic overexpression, of selected Mad family members in mice. (2) Test the hypothesis that Mad family members control the proliferation and cell growth (cell size, protein synthesis) of T Iymphocytes during T cell activation. We will examine the functional consequences of Mad overexpression or loss on cell division, cell size, RNA processing, and protein synthesis in primary lymphocytes immediately following activation. (3) Test the hypothesis that Mad directly binds and modulates the expression of essential genes involved in cell growth control. We will determine if Mad1 inhibits the expression of several essential genes involved in cell growth control. We will then use chromatin immunoprecipitation assays to determine if the regulatory regions of these genes are directly bound by Mad proteins. Together, these aims will test the overall hypothesis that Mad-Max complexes normally modulate lymphocyte proliferation and development in part by controlling the expression of growth-regulating genes. Results of these studies will identify target genes that could be manipulated to regulate the balance between Myc and Mad in order to inhibit lymphocyte proliferation in lymphomas or autoimmune disease, or to enhance clonal expansion of antigen-specific lymphocytes in a primary immune response, or following bone marrow transplantation.