Laboratoire de Biologie Structurale de la Cellule (BIOC), CNRS, Ecole polytechnique, Institut Polytechnique de Paris, Palaiseau, France.
Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, PSL Research University, Paris, France.
PLoS Biol. 2024 Sep 27;22(9):e3002821. doi: 10.1371/journal.pbio.3002821. eCollection 2024 Sep.
The nonsense-mediated mRNA decay (NMD) pathway clears eukaryotic cells of mRNAs containing premature termination codons (PTCs) or normal stop codons located in specific contexts. It therefore plays an important role in gene expression regulation. The precise molecular mechanism of the NMD pathway has long been considered to differ substantially from yeast to metazoa, despite the involvement of universally conserved factors such as the central ATP-dependent RNA-helicase Upf1. Here, we describe the crystal structure of the yeast Upf1 bound to its recently identified but yet uncharacterized partner Nmd4, show that Nmd4 stimulates Upf1 ATPase activity and that this interaction contributes to the elimination of NMD substrates. We also demonstrate that a region of Nmd4 critical for the interaction with Upf1 in yeast is conserved in the metazoan SMG6 protein, another major NMD factor. We show that this conserved region is involved in the interaction of SMG6 with UPF1 and that mutations in this region affect the levels of endogenous human NMD substrates. Our results support the universal conservation of the NMD mechanism in eukaryotes.
无意义介导的 mRNA 降解（NMD）途径清除真核细胞中含有提前终止密码子（PTC）或位于特定环境中的正常终止密码子的 mRNA。因此，它在基因表达调控中起着重要作用。尽管涉及普遍保守的因素，如中央 ATP 依赖性 RNA 解旋酶 Upf1，但 NMD 途径的精确分子机制长期以来一直被认为在酵母到后生动物之间存在很大差异。在这里，我们描述了酵母 Upf1 与其最近鉴定但尚未表征的伙伴 Nmd4 结合的晶体结构，表明 Nmd4 刺激 Upf1 ATP 酶活性，并且这种相互作用有助于消除 NMD 底物。我们还证明了 Nmd4 与酵母中 Upf1 相互作用的关键区域在另一个主要的 NMD 因子后生动物 SMG6 蛋白中保守。我们表明，这个保守区域参与了 SMG6 与 UPF1 的相互作用，并且该区域的突变会影响内源性人 NMD 底物的水平。我们的结果支持真核生物中 NMD 机制的普遍保守性。
