m6A RNA Degradation Products Are Catabolized by an Evolutionarily Conserved N6-Methyl-AMP Deaminase in Plant and Mammalian Cells
m6A RNA Degradation Products Are Catabolized by an Evolutionarily Conserved N6-Methyl-AMP Deaminase in Plant and Mammalian Cells
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DOI：
10.1105/tpc.18.00236
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发表时间：
2018-07-01
期刊：
影响因子：
11.6
通讯作者：
Witte, Claus-Peter
中科院分区：
文献类型：
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作者：
Chen, Mingjia;Urs, Mounashree J.;Witte, Claus-Peter
N-6-甲基腺嘌呤(m(6)A)是真核生物中最常见的转录后修饰。RNA的周转产生N-6-甲基化的AMP(N-6-MAMP)，其代谢去向不明。我们发现拟南芥和人类细胞需要N-6-MAMP脱氨酶(ADAL，更名为MAPDA)在体内通过水解性去除氨基甲基将N-6-MAMP分解为肌苷一磷酸。系统发育、结构和生化分析表明，许多真菌部分或完全缺乏MAPDA，这与这些生物中N(6)A-RNA甲基化的次要作用相吻合。MAPDA可能保护RNA免受m(6)A误掺入。这是必需的，因为真核RNA聚合酶可以使用N-6-mATP作为底物。去除MAPDA后，拟南芥的根生长略有减少，N-6-甲基腺苷、N-6-MAMP和N-6-mATP的浓度增加。虽然这可能会导致m(6)A错误掺入RNA，但我们表明，该频率太低，无法在体内可靠地检测到。由于N-6-MAMP在MAPDA突变体中的丰度是N-6-mATP的几倍，我们推测额外的分子过滤器抑制了N-6-mATP的产生。酶动力学数据表明，腺苷酸激酶代表了这种过滤器，对AMP和N-6-MAMP的磷酸化具有高度的选择性。我们得出的结论是，多层分子保护系统已经到位，防止了N-6-MAMP的积聚和回收。
N-6-methylated adenine (m(6)A) is the most frequent posttranscriptional modification in eukaryotic mRNA. Turnover of RNA generates N-6-methylated AMP (N-6-mAMP), which has an unclear metabolic fate. We show that Arabidopsis thaliana and human cells require an N-6-mAMP deaminase (ADAL, renamed MAPDA) to catabolize N-6-mAMP to inosine monophosphate in vivo by hydrolytically removing the aminomethyl group. A phylogenetic, structural, and biochemical analysis revealed that many fungi partially or fully lack MAPDA, which coincides with a minor role of N(6)A-RNA methylation in these organisms. MAPDA likely protects RNA from m(6)A misincorporation. This is required because eukaryotic RNA polymerase can use N-6-mATP as a substrate. Upon abrogation of MAPDA, root growth is slightly reduced, and the N-6-methyladenosine, N-6-mAMP, and N-6-mATP concentrations are increased in Arabidopsis. Although this will potentially lead to m(6)A misincorporation into RNA, we show that the frequency is too low to be reliably detected in vivo. Since N-6-mAMP was severalfold more abundant than N-6-mATP in MAPDA mutants, we speculate that additional molecular filters suppress the generation of N-6-mATP. Enzyme kinetic data indicate that adenylate kinases represent such filters being highly selective for AMP versus N-6-mAMP phosphorylation. We conclude that a multilayer molecular protection system is in place preventing N-6-mAMP accumulation and salvage.