An Atypical E3 Ligase Module in UBR4 Mediates Destabilization of N-degron Substrates
An Atypical E3 Ligase Module in UBR4 Mediates Destabilization of N-degron Substrates
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DOI：
10.1101/2023.05.08.539884
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发表时间：
2023-05
期刊：
影响因子：
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通讯作者：
Lucy Barnsby-Greer;P. D. Mabbitt;M. Déry;Daniel R. Squair;N. Wood;S. Lange;S. Virdee
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文献类型：
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作者：
Lucy Barnsby-Greer;P. D. Mabbitt;M. Déry;Daniel R. Squair;N. Wood;S. Lange;S. Virdee
UBR4 是 N-降解决定子途径的 E3 连接酶 (E3)，参与神经发育、年龄相关性肌肉萎缩和癌症进展。 600 kDa 蛋白 UBR4 中 E3 模块的位置和机制分类仍然未知。在此，我们在生化和结构水平上鉴定并表征了人类 UBR4 中的一个独特的 E3 模块，该模块由一个新的“hemiRING”锌指、一个富含螺旋的 UBR 锌指相互作用 (UZI) 子结构域和一个预测的背面相互作用 N 端螺旋组成。 E2 缀合酶 (E2)-E3 复合物的结构提供了原子水平的洞察，以了解 hemiring 对 E2s UBE2A/B 的精确特异性。 UZI 子结构域可以被认为是 E3 模块的一个组成部分，因为它对泛素负载的 E2 (E2∼Ub) 有适度的激活作用，而 UBE2A 固有的高赖氨酸反应性补充了这一作用。这些发现揭示了神经元 N-降解决定子 E3 连接酶的机制基础、其对 UBE2A 的特异性募集，并强调了与泛素 E3 活性相关的交叉支撑结构域的结构多样性未被充分认识。
UBR4 is an E3 ligase (E3) of the N-degron pathway and is involved in neurodevelopment, age-associated muscular atrophy and cancer progression. The location and mechanistic classification of the E3 module within the 600 kDa protein UBR4 remains unknown. Herein, we identify and characterize, at a biochemical and structural level, a distinct E3 module within human UBR4 consisting of a novel “hemiRING” zinc finger, a helical-rich UBR Zinc-finger Interacting (UZI) subdomain, and a predicted backside interacting N-terminal helix. A structure of an E2 conjugating enzyme (E2)-E3 complex provides atomic level insight into the exquisite specificity of the hemiRING towards the E2s UBE2A/B. The UZI subdomain can be considered a component of the E3 module as it has a modest activating effect on the ubiquitin loaded E2 (E2∼Ub), which is complemented by the intrinsically high lysine reactivity of UBE2A. These findings reveal the mechanistic underpinnings of a neuronal N-degron E3 ligase, its specific recruitment of UBE2A, and highlight the underappreciated architectural diversity of cross-brace domains associated with ubiquitin E3 activity.