Hypomodified tRNA in evolutionarily distant yeasts can trigger rapid tRNA decay to activate the general amino acid control response, but with different consequences
Hypomodified tRNA in evolutionarily distant yeasts can trigger rapid tRNA decay to activate the general amino acid control response, but with different consequences
复制标题
DOI：
10.1371/journal.pgen.1008893
复制
发表时间：
2020-08-01
期刊：
影响因子：
4.5
通讯作者：
Phizicky, Eric M.
中科院分区：
文献类型：
--
作者：
De Zoysa, Thareendra;Phizicky, Eric M.
tRNA修饰是高度保守的，缺乏tRNA修饰常常导致酵母、酿酒酵母和人类神经系统疾病的生长缺陷。酿酒酵母有两条tRNA质量控制衰变途径，它们在tRNA主体中感知缺乏修饰的tRNA。其中之一，快速tRNA衰变（RTD）途径，针对成熟tRNA通过Rat1和Xrn1进行5‘-3’外核溶解衰变。目前尚不清楚RTD是否在真核生物中保守，以及它是否可以解释与身体修饰缺陷相关的表型。在这里，我们关注的是进化上遥远的酵母——裂糖酵母（schizosaccharomyces pombe）中缺少m(7)G（46）的8个Delta突变体。m(7)G的损耗导致温度敏感性和RTD inS。人类的小头畸形原始侏儒症，以及小鼠的缺陷干细胞更新。我们展示了这一点。pombe trm8 Delta突变体由于tY（GUA）被Rat1/Dhp1衰变而对温度敏感，这意味着RTD在不同的真核生物中具有保守性。我们还表明，RTD的发作触发了两个pombeands的一般氨基酸控制（GAAC）途径的激活。导致进一步的tRNA损失。减少tRNA的损失。我们推测RTD及其GAAC调控将在包括人类在内的真核生物中广泛保守。所有trna都被广泛修饰，修饰缺陷通常会导致出芽酵母（酿酒酵母）的生长缺陷，以及人类的神经或其他疾病。InS。然而，缺乏任何一种tRNA修饰会导致某些成熟tRNA通过5‘-3’外切酶Rat1和Xrn1快速衰变（RTD）。由于tRNA质量控制衰变机制在其他真核生物中尚未得到广泛研究，我们研究了进化距离较远的分裂酵母——裂糖酵母（schizosaccharomyces pombe）中的trm8 Delta突变体，这些突变体在其tRNA的G(46)(m（7)G(46)）处缺乏7-甲基鸟苷。我们在此报道。pombe trm8 Delta突变体主要由于tRNA（Tyr(GUA)）的衰变而对温度敏感，而theRAT1orthologdhp1（+）的自发突变恢复了温度抗性并阻止了tRNA的衰变，证明了RTD途径的保守性。我们还首次报道了将RTD与一般氨基酸控制（GAAC）途径联系起来的证据，我们在s.p ombeands.c erevisiae中都发现了这一途径。InS。在trm8 δ突变体中，自发GAAC突变恢复了耐温性和tRNA水平，并且trm8 δ温度敏感性与tRNA（Tyr(GUA)）衰变导致的GAAC激活精确相关。同样，在那些学习良好的人身上。cerevisiae trm8 Delta trm4 Delta RTD突变体，由于tRNA（Val(AAC)）衰减，温度敏感性与GAAC激活密切相关；然而,inS。在酿酒酵母中，GAAC突变增加了tRNA的损失并加剧了温度敏感性。在GAAC突变inS上也发生了类似的加重生长缺陷。cerevisiae trm8 Delta和其他触发RTD的单修饰突变体。因此，这些结果表明，在s . pombeands中，GAAC的保守活化与RTD一致。但在两种生物体中GAAC反应的影响相反。我们推测RTD途径及其对GAAC途径的调控在真核生物中广泛保守，延伸到其他影响tRNA小体修饰的突变体中。
Author summary tRNA modifications are highly conserved and their lack frequently results in growth defects in the yeastSaccharomyces cerevisiaeand neuorological disorders in humans.S.cerevsiaiehas two tRNA quality control decay pathways that sense tRNAs lacking modifications in the main tRNA body. One of these, the rapid tRNA decay (RTD) pathway, targets mature tRNAs for 5'-3' exonucleolytic decay by Rat1 and Xrn1. It is unknown if RTD is conserved in eukaryotes, and if it might explain phenotypes associated with body modification defects. Here we focus ontrm8 Delta mutants, lacking m(7)G(46), in the evolutionarily distant yeastSchizosaccharomyces pombe. Loss of m(7)G causes temperature sensitivity and RTD inS.cerevisiae, microcephalic primordial dwarfism in humans, and defective stem cell renewal in mice. We show thatS.pombe trm8 Delta mutants are temperature sensitive due to tY(GUA) decay by Rat1/Dhp1, implying conservation of RTD among divergent eukaryotes. We also show that the onset of RTD triggers activation of the general amino acid control (GAAC) pathway in bothS.pombeandS.cerevisiae, resulting in further tRNA loss inS.pombeand reduced tRNA loss inS.cerevisiae. We speculate that RTD and its GAAC regulation will be widely conserved in eukaryotes including humans.All tRNAs are extensively modified, and modification deficiency often results in growth defects in the budding yeastSaccharomyces cerevisiaeand neurological or other disorders in humans. InS.cerevisiae, lack of any of several tRNA body modifications results in rapid tRNA decay (RTD) of certain mature tRNAs by the 5'-3' exonucleases Rat1 and Xrn1. As tRNA quality control decay mechanisms are not extensively studied in other eukaryotes, we studiedtrm8 Delta mutants in the evolutionarily distant fission yeastSchizosaccharomyces pombe, which lack 7-methylguanosine at G(46)(m(7)G(46)) of their tRNAs. We report here thatS.pombe trm8 Delta mutants are temperature sensitive primarily due to decay of tRNA(Tyr(GUA))and that spontaneous mutations in theRAT1orthologdhp1(+)restored temperature resistance and prevented tRNA decay, demonstrating conservation of the RTD pathway. We also report for the first time evidence linking the RTD and the general amino acid control (GAAC) pathways, which we show in bothS.pombeandS.cerevisiae. InS.pombe trm8 Delta mutants, spontaneous GAAC mutations restored temperature resistance and tRNA levels, and thetrm8 Delta temperature sensitivity was precisely linked to GAAC activation due to tRNA(Tyr(GUA))decay. Similarly, in the well-studiedS.cerevisiae trm8 Delta trm4 Delta RTD mutant, temperature sensitivity was closely linked to GAAC activation due to tRNA(Val(AAC))decay; however, inS.cerevisiae, GAAC mutations increased tRNA loss and exacerbated temperature sensitivity. A similar exacerbated growth defect occurred upon GAAC mutation inS.cerevisiae trm8 Delta and other single modification mutants that triggered RTD. Thus, these results demonstrate a conserved GAAC activation coincident with RTD inS.pombeandS.cerevisiae, but an opposite impact of the GAAC response in the two organisms. We speculate that the RTD pathway and its regulation of the GAAC pathway is widely conserved in eukaryotes, extending to other mutants affecting tRNA body modifications.