PDF(Pubmed)
Abstract：
The most abundant N6-methyladenosine (m6A) modification on mRNAs is installed non-stoichiometrically across transcripts, with 5\' untranslated regions (5\' UTRs) being the least conductive. 5\' UTRs are essential for translation initiation, yet the molecular mechanisms orchestrated by m6A remain poorly understood. Here, we combined structural, biochemical, and single-molecule approaches and show that at the most common position, a single m6A does not affect translation yields, the kinetics of translation initiation complex assembly, or start codon recognition both under permissive growth and following exposure to oxidative stress. Cryoelectron microscopy (cryo-EM) structures of the late preinitiation complex reveal that m6A purine ring established stacking interactions with an arginine side chain of the initiation factor eIF2α, although with only a marginal energy contribution, as estimated computationally. These findings provide molecular insights into m6A interactions with the initiation complex and suggest that the subtle stabilization is unlikely to affect the translation dynamics under homeostatic conditions or stress.
摘要：
mRNA上最丰富的N6-甲基腺苷（m6A）修饰在转录本上非化学计量地安装，其中5个非翻译区域(5个UTR)导电率最低。5UTR对于翻译启动至关重要，然而，由m6A协调的分子机制仍然知之甚少。这里,我们结合了结构，生物化学，和单分子方法，并表明在最常见的位置，单个M6A不会影响翻译产量，平移起始复杂装配的动力学，或在允许生长和暴露于氧化应激后的起始密码子识别。晚期预起始复合物的冷冻电子显微镜（cryo-EM）结构显示，m6A嘌呤环与起始因子eIF2α的精氨酸侧链建立了堆叠相互作用，虽然只有边际能源贡献，根据计算估计。这些发现提供了对m6A与起始复合物相互作用的分子见解，并表明在稳态条件或压力下，微妙的稳定不太可能影响翻译动力学。
