Zebrafish rbm8a and magoh mutants reveal EJC developmental functions and new 3′UTR intron-containing NMD targets
Zebrafish rbm8a and magoh mutants reveal EJC developmental functions and new 3′UTR intron-containing NMD targets
复制标题
DOI：
10.1371/journal.pgen.1008830
复制
发表时间：
2020-06-01
期刊：
影响因子：
4.5
通讯作者：
Singh, Guramrit
中科院分区：
文献类型：
--
作者：
Gangras, Pooja;Gallagher, Thomas L.;Singh, Guramrit
许多转录后机制通过mRNA 3UTR来调节蛋白质表达，这种控制对于发育至关重要。我们发现，两个斑马鱼外显子连接复合体（EJC）核心基因rbm 8a和magoh的纯合突变导致肌肉组织解体，神经细胞死亡，运动神经元生长缺陷，以及由于翻译终止>= 50 nts上游的最后一个外显子-外显子连接的无义介导的mRNA衰减（NMD）的mRNA的失调。有趣的是，我们发现EJC依赖的NMD也调节包含终止密码子下游< 50 nt的3 ' UTR内含子（3 ' UI）的转录物的子集。含有这种终止密码子近端3 ' UI的一些转录物在培养的人细胞和小鼠胚胎干细胞中也是NMD敏感的。我们鉴定了167个在斑马鱼、小鼠和人类中含有保守的近端3 ' UI的基因。foxo 3b是一种这样的近端3 ′端含UI的基因，其在斑马鱼EJC突变胚胎中在mRNA和蛋白质水平上均被上调，并且在EJC突变胚胎中foxo 3b功能的丧失显著地挽救了运动轴突生长缺陷。这些数据与EJC依赖的NMD调节foxo 3b mRNA以控制斑马鱼发育期间的蛋白质表达一致。我们的工作表明EJC对斑马鱼的正常发育至关重要，并表明近端3 'UI可能在脊椎动物中发挥基因调控功能。
Many post-transcriptional mechanisms operate via mRNA 3UTRs to regulate protein expression, and such controls are crucial for development. We show that homozygous mutations in two zebrafish exon junction complex (EJC) core genes rbm8a and magoh leads to muscle disorganization, neural cell death, and motor neuron outgrowth defects, as well as dysregulation of mRNAs subjected to nonsense-mediated mRNA decay (NMD) due to translation termination >= 50 nts upstream of the last exon-exon junction. Intriguingly, we find that EJC-dependent NMD also regulates a subset of transcripts that contain 3 ' UTR introns (3 ' UI) < 50 nts downstream of a stop codon. Some transcripts containing such stop codon-proximal 3 ' UI are also NMD-sensitive in cultured human cells and mouse embryonic stem cells. We identify 167 genes that contain a conserved proximal 3 ' UI in zebrafish, mouse and humans. foxo3b is one such proximal 3 ' UI-containing gene that is upregulated in zebrafish EJC mutant embryos, at both mRNA and protein levels, and loss of foxo3b function in EJC mutant embryos significantly rescues motor axon growth defects. These data are consistent with EJC-dependent NMD regulating foxo3b mRNA to control protein expression during zebrafish development. Our work shows that the EJC is critical for normal zebrafish development and suggests that proximal 3 ' UIs may serve gene regulatory function in vertebrates.