Role of Alternative Mxi1 Isoforms in the Myc Network

描述：(申请人提供)MYC原癌基因家族在 在对有丝分裂刺激的反应和控制中的中心作用 正常细胞和恶性细胞的增殖。C-Myc蛋白过度表达是一种 Burkitt淋巴瘤的特征，N-myc扩增是一个关键 神经母细胞瘤的预后因素。MYC基因的表达也在 许多其他癌症，但调节Myc活性的分子机制是 只有一部分得到了澄清。这项提案将专门调查 MxII和MxiO这两个Myc家族成员在调节两种c- 和N-Myc.作为一种转录因子，Myc调控相关基因的表达 对细胞生长、分裂和凋亡的影响。与Myc不同，Mxii抑制 转录一些Myc调控的基因，抵消Myc的影响。 因此，Mxii是Myc拮抗剂。我们已经证明了MxII的表达会导致 生长停滞，抑制细胞体外增殖。因此，我们 假设MxII活性降低可能会增强Myc依赖 扩散。我们最近发现了一部小说MxiO，它是一部交替转录的 缺乏MxII生长抑制活性的MxII亚型。而MxiO和 MxII在许多细胞系和组织中同时表达，相对的 MxiO在肿瘤和肿瘤细胞系中的水平高于正常细胞。 MxiO和MxII水平的这种变化表明Myc抑制 MxII的活性可能受MxiO的调节。我们假设Mxio是Mxii 对抗者。这种单一基因产生蛋白质产物的概念 在Bclx的情况下，替代的生物活性被很好地建立起来 (bcl-xl vs.bc-xs)和Ink4a(p16 vs.p14)。在这项提案中，我们将探索 语境中MxiO和Mxil之间的相互作用以及与Myc的相互作用 细胞增殖和肿瘤，通过设置以下特定的 目的：(1)表征MxiO的生物活性；(2)确定如何 利用我们的经验，MxiO和MxII的表达是协调调控的 利用MxII启动子来确定调控表达的因素 通过MxiO启动子；(3)确定生长调控机制。 Mxio和Mxii在Myc的背景下-我们将使用c-Myc诱导的模型 转化以及N-Myc依赖的神经母细胞瘤增殖 探索这些相互作用，并研究基因表达的模式；以及(4) 特异性灭活MxII或MxiO的体内实验研究 转基因小鼠。通过这些研究，我们将更好地了解 这些MxII亚型在复杂的Myc信号通路中的作用 在细胞生长调节和肿瘤形成方面。

DESCRIPTION: (provided by applicant) The MYC proto-oncogene family plays a central role in the response to mitogenic stimuli and the control of proliferation in normal and malignant cells. c-Myc protein overexpression is a hallmark of Burkitt's lymphoma, and N-MYC amplification is a critical prognostic factor in neuroblastoma. MYC gene expression is also deregulated in many other cancers, but the molecular mechanisms that regulate Myc activity are only partly elucidated. This proposal will specifically investigate the role of Mxii and MxiO, two Myc family members, in modulating the activity of both c- and N-Myc. As a transcription factor, Myc regulates expression of genes related to cell growth, division and apoptosis. In contrast to Myc, Mxii represses transcription of some Myc-regulated genes, counteracting the effects of Myc. Thus, Mxii is a Myc antagonist. We have shown that Mxii expression results in growth arrest, suppressing cell proliferation in vitro. Therefore, we hypothesize that reduced Mxii activity is likely to potentiate Myc-dependent proliferation. We recently identified MxiO, a novel, alternatively transcribed Mxii isoform that lacks the growth suppressive activity of Mxii. While MxiO and Mxii are concomitantly expressed in many cell lines and tissues, the relative levels of MxiO are higher in tumors and tumor cell lines than in normal cells. This variation in levels of MxiO and Mxii suggests that the Myc-inhibitory activity of Mxii may be modulated by MxiO. We postulate that MxiO is an Mxii antagonist. This notion of a single gene giving rise to protein products with alternative biological activities is well established in the case of Bcl-x (Bcl-xL vs. Bcl-xS) and Ink4a (p16 vs. p14). In this proposal, we will explore the interactions of MxiO and Mxil with each other and with Myc, in the context of both cell proliferation and neoplasia, by setting the following Specific Aims: (1) Characterize the biological activity of MxiO; (2) Determine how expression of MxiO and Mxii are coordinately regulated, using our experience with the Mxii promoter to determine the factors that regulate expression through the MxiO promoter; (3) Determine mechanisms of growth regulation by MxiO and Mxii in the context of Myc-we will use models of c-Myc-induced transformation, as well as N-Myc-dependent neuroblastoma proliferation to explore these interactions, and also study patterns of gene expression; and (4) Evaluate the in vivo effects of specifically inactivating mxii or mxiO in transgenic mice. Through these studies, we will gain a better understanding of the role of these Mxii isoforms in the complex Myc signaling pathways involved in cell growth regulation and neoplasia.