Andreev Dmitry E, O'Connor Patrick B F, Fahey Ciara, Kenny Elaine M, Terenin Ilya M, Dmitriev Sergey E, Cormican Paul, Morris Derek W, Shatsky Ivan N, Baranov Pavel V
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland.
Elife. 2015 Jan 26;4:e03971. doi: 10.7554/eLife.03971.
Eukaryotic cells rapidly reduce protein synthesis in response to various stress conditions. This can be achieved by the phosphorylation-mediated inactivation of a key translation initiation factor, eukaryotic initiation factor 2 (eIF2). However, the persistent translation of certain mRNAs is required for deployment of an adequate stress response. We carried out ribosome profiling of cultured human cells under conditions of severe stress induced with sodium arsenite. Although this led to a 5.4-fold general translational repression, the protein coding open reading frames (ORFs) of certain individual mRNAs exhibited resistance to the inhibition. Nearly all resistant transcripts possess at least one efficiently translated upstream open reading frame (uORF) that represses translation of the main coding ORF under normal conditions. Site-specific mutagenesis of two identified stress resistant mRNAs (PPP1R15B and IFRD1) demonstrated that a single uORF is sufficient for eIF2-mediated translation control in both cases. Phylogenetic analysis suggests that at least two regulatory uORFs (namely, in SLC35A4 and MIEF1) encode functional protein products.
真核细胞会对各种应激条件做出反应,迅速降低蛋白质合成。这可以通过磷酸化介导的关键翻译起始因子——真核起始因子2(eIF2)失活来实现。然而,为了部署充分的应激反应,某些mRNA的持续翻译是必需的。我们在用亚砷酸钠诱导的严重应激条件下,对培养的人类细胞进行了核糖体分析。尽管这导致了5.4倍的总体翻译抑制,但某些单个mRNA的蛋白质编码开放阅读框(ORF)表现出对抑制的抗性。几乎所有抗性转录本都至少拥有一个在正常条件下抑制主要编码ORF翻译的有效翻译上游开放阅读框(uORF)。对两个已鉴定的应激抗性mRNA(PPP1R15B和IFRD1)进行的位点特异性诱变表明,在这两种情况下,单个uORF足以实现eIF2介导的翻译控制。系统发育分析表明,至少两个调节性uORF(即SLC35A4和MIEF1中的uORF)编码功能性蛋白质产物。