Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA.
Department of Computer Science, University of Central Florida, Orlando, FL 32816, USA.
Nucleic Acids Res. 2019 Nov 4;47(19):10373-10387. doi: 10.1093/nar/gkz761.
U2 auxiliary factor 1 (U2AF1) functions in 3'-splice site selection during pre-mRNA processing. Alternative usage of duplicated tandem exons in U2AF1 produces two isoforms, U2AF1a and U2AF1b, but their functional differences are unappreciated due to their homology. Through integrative approaches of genome editing, customized-transcriptome profiling and crosslinking-mediated interactome analyses, we discovered that the expression of U2AF1 isoforms is controlled by mTOR and they exhibit a distinctive molecular profile for the splice site and protein interactomes. Mechanistic dissection of mutually exclusive alternative splicing events revealed that U2AF1 isoforms' inherent differential preferences of nucleotide sequences and their stoichiometry determine the 3'-splice site. Importantly, U2AF1a-driven transcriptomes feature alternative splicing events in the 5'-untranslated region (5'-UTR) that are favorable for translation. These findings unveil distinct roles of duplicated tandem exon-derived U2AF1 isoforms in the regulation of the transcriptome and suggest U2AF1a-driven 5'-UTR alternative splicing as a molecular mechanism of mTOR-regulated translational control.
U2 辅助因子 1（U2AF1）在 pre-mRNA 加工过程中的 3'-剪接位点选择中发挥作用。U2AF1 中重复串联外显子的选择性使用产生了两种异构体，U2AF1a 和 U2AF1b，但由于它们的同源性，它们的功能差异尚未得到重视。通过基因组编辑、定制转录组谱分析和交联介导的互作分析的综合方法，我们发现 U2AF1 异构体的表达受 mTOR 控制，它们在剪接位点和蛋白质互作组方面表现出独特的分子特征。对互斥选择性剪接事件的机制分析表明，U2AF1 异构体核苷酸序列的固有差异偏好及其化学计量决定了 3'-剪接位点。重要的是，U2AF1a 驱动的转录组具有有利于翻译的 5'-非翻译区（5'-UTR）中的选择性剪接事件。这些发现揭示了重复串联外显子衍生的 U2AF1 异构体在转录组调控中的不同作用，并表明 U2AF1a 驱动的 5'-UTR 选择性剪接是 mTOR 调控翻译控制的分子机制。
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