Molecular Mechanisms of eIF4E mediated transformation.

描述（由申请人提供）：真核翻译起始因子eIF 4 E是细胞生长的关键调节因子，在包括一些白血病和乳腺癌在内的几种癌症中升高。eIF 4 E在细胞中的过表达促进增殖和随后的转化。eIF 4 E是RNA调节子中的网络节点，通过协调上调参与这些途径的基因的表达来促进增殖和存活。eIF 4 E在细胞核和细胞质中均起作用。在细胞质中，它结合在mRNA的5'端上发现的7甲基鸟苷（m7 G）帽，从而允许翻译起始。重要的是，高达68%的eIF 4 E在细胞核中发现，在那里它促进包括细胞周期蛋白D1，A2，B1，mdm 2，c-myc等的生长促进转录子的mRNA输出。我们在靶mRNA的非翻译区鉴定了一个50个核苷酸的元件，其赋予eIF 4 E敏感性（允许优先输出），并将其称为eIF 4 E敏感性元件（4 E-SE）。因此，eIF 4 E可以协同上调含有4 E-SE的基因的表达。eIF 4 E在白血病的一个亚组中在（至少）三个水平上失调：eIF 4 E高度升高，其亚细胞分布改变，其中其在细胞核中积累，并且通过结合伴侣对其活性的调节改变。在这里，我们将研究这种失调的分子基础。此外，我们将确定这种失调对eIF 4 E功能的影响。我们确定了一种新的方法来提高eIF 4 E水平，通过增加eIF 4 E mRNA的稳定性，通过与mRNA的稳定性因子HuR的相互作用。与eIF 4 E一样，HuR是一种有效的原癌基因。接下来，我们将研究细胞用于调节eIF 4 E的定位和功能的方法，以及这是否在这些癌症中失调。最后，我们将研究eIF 4 E的新核伙伴对其活动的影响。我们提出了三个具体的目标来研究这些可能性：1。确定HuR是否调节eIF 4 E的活性2.确定eIF 4 E转运蛋白4 E-T是否调节eIF 4 E功能及其定位，3.检查通过eIF 4 E结合蛋白BP 1控制核eIF 4 E的新模式。我们相信，阐明这一调控网络将产生新的见解eIF 4 E介导的转化。此外，这些发现可以为以eIF 4 E失调为特征的癌症提供新的治疗策略。公共卫生相关性：真核翻译起始因子eIF 4 E在许多人类癌症中失调，包括乳腺癌、头颈癌、结肠癌、前列腺癌和血癌。我们的项目旨在了解这种失调的机制和治疗意义。

DESCRIPTION (provided by applicant): The eukaryotic translation initiation factor eIF4E, a key modulator of cellular growth, is elevated in several cancers including some leukemias and breast cancer. eIF4E overexpression in cells promotes proliferation and subsequently transformation. eIF4E is a network node in a RNA regulon promoting proliferation and survival by the coordinated upregulation of the expression of genes involved in these pathways. eIF4E functions in both the nucleus and cytoplasm. In the cytoplasm, it binds the 7 methyl guanosine (m7G) cap found on the 5' end of mRNAs thereby allowing translation initiation. Importantly, up to 68% of eIF4E is found in the nucleus, where it promotes mRNA export of a subset of growth promoting transcripts including cyclins D1, A2, B1, mdm2, c-myc etc. This mRNA export activity contributes substantially to its transformation activity. We identified a 50 nucleotide element in the untranslated region of target mRNAs which impart sensitivity to eIF4E (allowing preferential export) and refer to this as an eIF4E sensitivity element (4E- SE). Thus, eIF4E can coordinately upregulate expression of genes which contain the 4E-SE. eIF4E is dysregulated at (least) three levels in a subset of leukemias: eIF4E is highly elevated, its subcellular distribution is altered where it accumulates in the nucleus and regulation of its activity by binding partners is altered. Here, we will examine the molecular basis for this dysregulation. Further we will determine the effects of this dysregulation on eIF4E function. We identified a novel means to elevate eIF4E levels, through increased eIF4E mRNA stability via interactions with the mRNA stability factor HuR. Like eIF4E, HuR is a potent proto-oncogene. Next, we will examine the means the cell uses to regulate localization and thus function of eIF4E and whether this is dysregulated in these cancers. Finally, we will examine the impact of a novel nuclear partner of eIF4E on its activities. We propose three specific aims to investigate these possibilities: 1. Establish whether HuR modulates eIF4E's activity 2. Establish whether the eIF4E transporter protein, 4E-T, modulates eIF4E function as well as its localization and 3. Examine novel modes of control of nuclear eIF4E by the eIF4E binding protein BP1. We believe that elucidation of this regulatory network will yield new insights into eIF4E mediated transformation. Further, these findings could provide novel therapeutic strategies for cancers characterized by dysregulated eIF4E. PUBLIC HEALTH RELEVANCE: The eukaryotic translation initiation factor eIF4E is dysregulated in many human cancers including cancers of the breast, head & neck, colon, prostate and blood. Our project is designed to understand the mechanisms and therapeutic implications of this dysregulation.