Abstract：
The yeast glucose-induced degradation-deficient (GID) E3 ubiquitin ligase forms a suite of complexes with interchangeable receptors that selectively recruit N-terminal degron motifs of metabolic enzyme substrates. The orthologous higher eukaryotic C-terminal to LisH (CTLH) E3 complex has been proposed to also recognize substrates through an alternative subunit, WDR26, which promotes the formation of supramolecular CTLH E3 assemblies. Here, we discover that human WDR26 binds the metabolic enzyme nicotinamide/nicotinic-acid-mononucleotide-adenylyltransferase 1 (NMNAT1) and mediates its CTLH E3-dependent ubiquitylation independently of canonical GID/CTLH E3-family substrate receptors. The CTLH subunit YPEL5 inhibits NMNAT1 ubiquitylation and cellular turnover by WDR26-CTLH E3, thereby affecting NMNAT1-mediated metabolic activation and cytotoxicity of the prodrug tiazofurin. Cryoelectron microscopy (cryo-EM) structures of NMNAT1- and YPEL5-bound WDR26-CTLH E3 complexes reveal an internal basic degron motif of NMNAT1 essential for targeting by WDR26-CTLH E3 and degron mimicry by YPEL5\'s N terminus antagonizing substrate binding. Thus, our data provide a mechanistic understanding of how YPEL5-WDR26-CTLH E3 acts as a modulator of NMNAT1-dependent metabolism.
摘要：
酵母葡萄糖诱导的降解缺陷型（GID）E3泛素连接酶与可互换的受体形成一套复合物，可选择性募集代谢酶底物的N末端degron基序。已提出LisH（CTLH）E3复合物的直系同源高等真核生物C末端也通过替代亚基识别底物，WDR26，促进超分子CTLHE3组件的形成。这里,我们发现,人WDR26与代谢酶烟酰胺/烟酸-单核苷酸-腺苷酰转移酶1(NMNAT1)结合,并介导其CTLHE3依赖性泛素化,而与规范的GID/CTLHE3家族底物受体无关.CTLH亚基YPEL5通过WDR26-CTLHE3抑制NMNAT1泛素化和细胞更新，从而影响NMNAT1介导的前体硫氮呋喃的代谢激活和细胞毒性。NMNAT1-和YPEL5结合的WDR26-CTLHE3复合物的冷冻电子显微镜（cryo-EM）结构揭示了NMNAT1的内部基本degron基序，这对于WDR26-CTLHE3的靶向和YPEL5的N末端拮抗底物结合的degron模仿至关重要。因此，我们的数据提供了对YPEL5-WDR26-CTLHE3如何充当NMNAT1依赖性代谢调节剂的机制理解.
