Structural basis for multi-subunit assembly and substrate selection by the E3 ligase NRBP1

泛素-蛋白酶体系统通过其选择性和程序性降解来调节蛋白质水平，因此涉及几乎所有的基本生物过程-例如DNA损伤和修复，细胞周期，细胞生长和增殖以及信号转导。该途径在疾病中通常失调，要么是由于未能标记病理蛋白质降解（错误的蛋白质控制系统），要么是由于错误地导致必要的蛋白质被破坏。泛素化机制需要酶蛋白E1和E2的合作，这有助于其通用性，允许跨越蛋白质组，以及E3连接酶，通过直接与其蛋白质底物相互作用赋予其特异性。我将通过X射线晶体学确定模块化E3连接酶NRBP 1和UBR 1的结构，它们与各自提出的底物BRI 2和RGS 4复合。互补技术，如蛋白质质谱，生物物理和细胞分析，并筛选可能的化学调节剂将帮助我们发现和扰动的结构基础的多亚基组装和底物选择这些E3连接酶。我的研究将进一步加深我们对泛素化机制调节的分子机制的理解，以及它对每个底物施加的精确时空控制，为随意重定向和干扰蛋白水解途径的新兴领域奠定基础。我的目标也阐明了阿尔茨海默病的发病机制，因为NRBP 1和UBR 1的蛋白质底物都与淀粉样疾病有关。

The ubiquitin-proteasome system regulates protein levels through their selective and programmed degradation and thus is implicated in almost all basic biological processes - such as DNA damage and repair, cell cycle, cell growth and proliferation and signal transduction. The pathway is often dysregulated in disease, either by failing to mark pathological proteins for degradation (faulty protein control system), or by erroneously leading necessary proteins to their destruction. The ubiquitylation machinery requires the cooperation of enzymatic proteins E1 and E2 that facilitate its universality allowing spanning of the proteome, and E3 ligases that confer its specificity by directly interacting with their protein substrates. I will determine the structure of the modular E3 ligases NRBP1 and UBR1, in complex with their respective proposed substrates BRI2 and RGS4 by X-ray crystallography. Complimentary techniques such as protein mass-spectrometry, biophysical and cellular assays, and screening of possible chemical modulators will help us uncover and perturb the structural basis of multi-subunit assembly and substrate selection of these E3 ligases. My studies will further our understanding of the molecular mechanisms underlying the regulation of ubiquitinylation machinery and the precise spatiotemporal control it exerts on each substrate, setting the foundations for the emerging field of re-directing and perturbing the proteolytic pathway at will. I aim to also shed light on the pathogenesis of Alzheimer's Disease, since both NRBP1 and UBR1's protein substrates have been implicated in amyloidogenic diseases.