Nutrient Regulation of Cell Physiology by O-GlcNAcylation

N-乙酰氨基葡萄糖对苏氨酸残基(O-GlcN酰化)的循环 线粒体蛋白作为营养感受器调节信号、转录和细胞 生理学。O-GlcN酰化异常是糖尿病、癌症和阿尔茨海默病的病因基础。 O-GlcN酰化几乎调控转录的方方面面，包括RNA聚合酶II、组蛋白、DNA 甲基转移酶，以及几乎所有的转录因子。然而，我们对这种机制知之甚少。 牵涉其中。塔塔结合蛋白(TBP)是转录过程中最重要的成分之一 机械设备。我们最近的研究表明，TBP受O-GlcN酰化调节，对营养做出反应。 O-GlcN酰化与蛋白质磷酸化和其他修饰有广泛的串扰。然而， 与由数百种激酶催化的磷酸化不同，只有一个高度保守的基因 编码O-GlcNAc转移酶(OGT)。尽管如此，OGT定点修饰了数千种蛋白质。 我们的数据表明，OGT的底物特异性不仅取决于它对多肽的特异性 序列，但也通过它与其他蛋白质的瞬时结合，这些蛋白质动态地将其定位于特定的 底物。OGT的靶向作用在很大程度上是由其四肽重复序列(TPR)介导的。OGT 缺失的TPR对小肽仍有活性，但对全长蛋白的活性很差。 在这里，我们将研究与O-GlcN酰化有关的两个主要问题：具体目标1：继续 研究TATA结合蛋白(TBP)O-GlcN酰化对血糖的调节。假设：at 某些启动子，葡萄糖调节TBP DNA结合及其通过改变其O-来弯曲DNA的能力 谷氨酰化。我们将系统地阐明TBP的这种营养调节的机制和功能。 三个目标：a.O-GlcN酰化在TBP的分子和细胞特性中的作用？B.O-的角色 GlcNAc参与TBP在转录循环中的相互作用。C.O-GlcNAc在TBP介导的体内作用中的作用 基因表达。具体目标2：继续阐明OGT的具体目标 成千上万种不同的蛋白质底物？假设：OGT实现了高度的特异性而不是 不仅是由于它对多肽序列的识别，而且还因为它被辅助物靶向底物 蛋白质。这一目标将系统地评估OGT结合伙伴的一般和具体作用 在OGT的活动中朝着它的许多底物。 鉴于O-GlcNAc对慢性疾病机制的重要性，例如糖尿病中的葡萄糖毒性， 癌症和神经退行性变，阐明这些机制不仅是理解 转录和信号传递，也是为了发现治疗的新途径。

The cycling of N-acetylglucosamine on Ser(Thr) residues (O-GlcNAcylation) of nuclear, cytoplasmic and mitochondrial proteins serves as a nutrient sensor to regulate signaling, transcription, and cellular physiology. Abnormal O-GlcNAcylation underlies the etiology of diabetes, cancer and Alzheimer's disease. O-GlcNAcylation regulates nearly every aspect of transcription, including RNA polymerase II, histones, DNA methyltransferases, and nearly all transcription factors. Yet we know very little about the mechanisms involved. TATA-binding protein (TBP) is amongst the most important components of the transcription machinery. Our recent studies indicate that TBP regulated by O-GlcNAcylation in response to nutrients. O-GlcNAcylation has extensive crosstalk with protein phosphorylation and other modifications. However, unlike phosphorylation, which is catalyzed by hundreds of kinases, there is only one highly conserved gene encoding O-GlcNAc transferase (OGT). Nonetheless, OGT site-specifically modifies thousands of proteins. Our data indicate that OGT's substrate specificity is not only determined by its specificity for peptide sequence, but also by its transient associations with other proteins, which dynamically target it to specific substrates. OGT targeting interactions are largely mediated by its tetratricopeptide repeats (TPRs). OGT missing TPRs remains active against small peptides, but has poor activity against full-length proteins. Herein we will investigate two major questions related to O-GlcNAcylation: Specific Aim 1: Continue to Study Glucose Regulation of TATA-binding protein (TBP) via its O-GlcNAcylation. Hypothesis: At certain promoters, glucose regulates TBP DNA-binding and its ability to bend DNA by altering its O- GlcNAcylation. We will systematically elucidate mechanisms and functions of this nutrient regulation of TBP. Three goals: A. Roles of O-GlcNAcylation in the molecular and cellular properties of TBP? B. Roles of O- GlcNAc in TBP's Interactions in the Transcription Cycle. C. O-GlcNAc's In Vivo Roles in TBP-mediated Gene Expression. Specific Aim 2: Continue to Elucidate How OGT is Specifically Targeted to Thousands of Different Protein Substrates? Hypothesis: OGT achieves a high degree of specificity not only by its recognition of peptide sequence, but also by it being targeted to substrates by accessory proteins. This Aim will systematically evaluate both the general and specific roles of OGT binding partners in OGT's activities toward its many substrates. Given O-GlcNAc's importance to mechanisms of chronic disease, such as glucose toxicity in diabetes, cancer and neurodegeneration, elucidation of these mechanisms will not only be key to understanding transcription and signaling, also to uncovering new avenues for therapeutics.