Stem Cell Program, Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA, 02115, USA.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA.
Nat Commun. 2022 Dec 23;13(1):7904. doi: 10.1038/s41467-022-35643-1.
N6-methyladenosine (mA), the most abundant modification of mRNA, is essential for normal development and dysregulation promotes cancer. mA is highly enriched in the 3' untranslated region (UTR) of a large subset of mRNAs to influence mRNA stability and/or translation. However, the mechanism responsible for the observed mA distribution remains enigmatic. Here we find the exon junction complex shapes the mA landscape by blocking METTL3-mediated mA modification close to exon junctions within coding sequence (CDS). Depletion of EIF4A3, a core component of the EJC, causes increased METTL3 binding and mA modification of short internal exons, and sites close to exon-exon junctions within mRNA. Reporter gene experiments further support the role of splicing and EIF4A3 deposition in controlling mA modification via the local steric blockade of METTL3. Our results explain how characteristic patterns of mA mRNA modification are established and uncover a role of the EJC in shaping the mA epitranscriptome.
N6-甲基腺苷（mA）是 mRNA 中最丰富的修饰物，对于正常发育至关重要，其失调会促进癌症发生。mA 在很大一部分 mRNA 的 3'非翻译区（UTR）中高度富集，以影响 mRNA 的稳定性和/或翻译。然而，负责观察到的 mA 分布的机制仍然是个谜。在这里，我们发现外显子结合复合物通过阻止 METTL3 介导的 mA 修饰来塑造 mA 景观，这种修饰靠近编码序列（CDS）中的外显子交界处。EJC 的核心组成部分 EIF4A3 的耗竭会导致 METTL3 结合和短内部外显子以及靠近 mRNA 中外显子-外显子交界处的 mA 修饰增加。报告基因实验进一步支持剪接和 EIF4A3 沉积通过 METTL3 的局部空间位阻来控制 mA 修饰的作用。我们的结果解释了如何建立 mA mRNA 修饰的特征模式，并揭示了 EJC 在塑造 mA 转录后组中的作用。
