In eukaryotic cells, protein synthesis typically begins with the binding of eIF4F to the 7-methylguanylate (m⁷G) cap found on the 5′ end of the majority of mRNAs. Surprisingly, overall translational output remains robust under eIF4F inhibition. The broad spectrum of eIF4F-resistant translatomes is incompatible with cap-independent translation mediated by internal ribosome entry sites (IRESs). Here, we report that N⁶-methyladenosine (m⁶A) facilitates mRNA translation that is resistant to eIF4F inactivation. Depletion of the methyltransferase METTL3 selectively inhibits translation of mRNAs bearing 5′ UTR methylation, but not mRNAs with 5′ terminal oligopyrimidine (TOP) elements. We identify ABCF1 as a critical mediator of m⁶A-promoted translation under both stress and physiological conditions. Supporting the role of ABCF1 in m⁶A-facilitated mRNA translation, ABCF1-sensitive transcripts largely overlap with METTL3-dependent mRNA targets. By illustrating the scope and mechanism of eIF4F-independent mRNA translation, these findings reshape our current perceptions of cellular translational pathways.

在真核细胞中，蛋白质合成通常始于 eIF4F与大多数 mRNA 的 5' 端发现的 7-甲基鸟苷酸 (m ⁷ G) 帽的结合。令人惊讶的是，在 eIF4F 抑制下，整体翻译输出保持稳健。广谱的 eIF4F 抗性翻译体与由内部核糖体进入位点 (IRES) 介导的不依赖帽的翻译不相容。在这里，我们报告N ⁶ -甲基腺苷 (m ⁶ A) 促进对 eIF4F 失活有抵抗力的 mRNA 翻译。甲基转移酶 METTL3 的消耗选择性抑制带有 5' UTR 甲基化的 mRNA 的翻译，但不抑制带有 5' 末端寡嘧啶 (TOP) 元件的 mRNA 的翻译。我们将 ABCF1 确定为 m ⁶的关键介质压力和生理条件下的 A 促进翻译。支持 ABCF1 在 m ⁶ A 促进的 mRNA 翻译中的作用，ABCF1 敏感的转录本在很大程度上与 METTL3 依赖的 mRNA 靶标重叠。通过说明不依赖于 eIF4F 的 mRNA 翻译的范围和机制，这些发现重塑了我们目前对细胞翻译途径的看法。