ELONGIN C: FUNCTION AND ROLE IN VHL DISEASE

许多证据表明，Elongin C是Elongin转录因子的一个调节亚基，在von Hippel-Landau蛋白(VHL)的肿瘤抑制功能中发挥着重要的作用，但与转录无关。这项建议的总体目标是确定Elongin C的生物学功能(S)及其在VHL肿瘤抑制中的作用。我们已经鉴定了Elongin C的酵母同源物，我们的理论基础是Elongin C的功能在哺乳动物细胞中将是保守的。我们的初步数据表明，酵母Elongin C与4种酵母蛋白：Snf4、Yap4、Yap6和Mdj1有很强的特异性相互作用。值得注意的是，这些Elongin C结合伙伴中的每一个都有一个哺乳动物同源物，并可以与特定的应激反应相关联。因此，我们的假设是Elongin C是应激反应中的一个关键蛋白质。这一假设将按照以下具体目标进行检验。具体目的1.研究酵母菌Elongin C在应激反应中的特性。初步研究表明，酵母Elongin C基因是非必需的，在正常细胞生长过程中低水平表达，该蛋白存在于细胞核和细胞质中。描述了评估低氧、营养和氧化应激对Elongin c缺失菌株的影响的实验。具体目的2.研究Elongin C与Snf4、Yap4、Yap6和Mdj1相互作用的性质和意义。Snf4是哺乳动物AMP活化蛋白激酶(AMPK)的伽马亚基的同源物。将评估Elongin C与Snf4结合对该激酶活性的影响。Yap4和Yap6是可能的转录因子，Mdj1是线粒体伴侣。这些蛋白与Elongin C之间的相互作用将识别与Elongin C平行或冗余的其他因子。描述了一种合成致死筛选，以确定可能弥补Elongin C VHL肿瘤抑制缺失的其他因子，阐明Elongin C的功能(S)可能导致发现治疗VHL疾病的新的治疗靶点。

Several lines of evidence indicate that Elongin C, a regulatory subunit of the Elongin transcription factor, plays an essential role, unrelated to transcription, in the tumor suppression function of the von Hippel-Landau protein (VHL). The overall objective of this proposal is to determine the biological function(s) of Elongin C and its role in VHL tumor suppression. We have identified the yeast homologue of Elongin C. Our rationale is that Elongin C function will be conserved in mammalian cells. Our preliminary data indicate that yeast Elongin C interacts strongly and specifically with 4 yeast proteins: Snf4, Yap4, Yap6 and Mdj1. Notably each of these Elongin C binding partners has a mammalian homologue and can be linked to specific stress responses. Thus our hypothesis is that Elongin C is a key protein in the stress response. This hypothesis will be examined as described in the following specific aims. Specific Aim 1. To characterize yeast Elongin C during the stress response. Preliminary studies indicate that the yeast Elongin C gene is non-essential, expressed at low levels during normal cell growth and that the protein is present in both the nucleus and in the cytoplasm. Experiments are described to assess the effects of hypoxic, nutrient, and oxidant stress in Elongin c null strains. Specific Aim 2. To examine the nature and significance of the Elongin C interactions with Snf4, Yap4, Yap6 and Mdj1. Snf4 is the homologue of the gamma subunit of mammalian AMP-activated protein kinase (AMPK). The affect of binding of Elongin C to Snf4 on the kinase activity will be assessed. Yap4 and Yap6 are putative transcription factors and Mdj1 is a mitochondrial chaperone. The interaction between these proteins and Elongin C will identify other factors that may operate in parallel or be redundant with Elongin C. A synthetic lethal screen is described to identify other factors that may compensate for absence of Elongin C VHL tumor suppression, the elucidation of the function(s) of Elongin C may lead to the identification of new therapeutic targets for treatment of VHL disease.