All tRNAs are extensively modified, and modification deficiency often results in growth defects in the budding yeast Saccharomyces cerevisiae and neurological or other disorders in humans. In S. 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 studied trm8Δ mutants in the evolutionarily distant fission yeast Schizosaccharomyces pombe, which lack 7-methylguanosine at G₄₆ (m⁷G₄₆) of their tRNAs. We report here that S. pombe trm8Δ mutants are temperature sensitive primarily due to decay of tRNA^Tyr(GUA) and that spontaneous mutations in the RAT1 ortholog dhp1⁺ 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 both S. pombe and S. cerevisiae. In S. pombe trm8Δ mutants, spontaneous GAAC mutations restored temperature resistance and tRNA levels, and the trm8Δ temperature sensitivity was precisely linked to GAAC activation due to tRNA^Tyr(GUA) decay. Similarly, in the well-studied S. cerevisiae trm8Δ trm4Δ RTD mutant, temperature sensitivity was closely linked to GAAC activation due to tRNA^Val(AAC) decay; however, in S. cerevisiae, GAAC mutations increased tRNA loss and exacerbated temperature sensitivity. A similar exacerbated growth defect occurred upon GAAC mutation in S. cerevisiae trm8Δ and other single modification mutants that triggered RTD. Thus, these results demonstrate a conserved GAAC activation coincident with RTD in S. pombe and S. 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.

所有的tRNA都经过广泛修饰，修饰缺陷通常会导致芽生啤酒酵母和人类神经系统疾病或其他疾病的生长缺陷。在S中。在酿酒酵母中，缺少任何几种tRNA主体修饰都会导致5'-3'外切核酸酶Rat1和Xrn1对某些成熟tRNA的快速tRNA衰减（RTD）。由于尚未在其他真核生物中广泛研究tRNA质量控制衰减机制，因此我们在进化距离较远的裂变酵母粟酒裂殖酵母中研究了trm8Δ突变体，该突变体在其tRNA的G ₄₆（m ⁷ G ₄₆）处缺少7-甲基鸟苷。我们在这里报告S。pombetrm8Δ突变体对温度敏感，这主要是由于tRNA ^{Tyr（GUA）的}衰减，而RAT1 ortholog dhp1 ⁺中的自发突变恢复了温度耐受性并阻止了tRNA的衰减，这表明RTD途径的保守性。我们还首次报告了将RTD与一般氨基酸控制（GAAC）途径相关联的证据，我们在S文献中均对此进行了展示。酵母和小号。啤酒酵母。在S中。pombetrm8Δ突变体，自发GAAC突变恢复了温度抗性和tRNA水平，并且trm8Δ温度敏感性与tAC ^Tyr（GUA）衰减引起的GAAC激活精确相关。同样，在经过充分研究的S中。酿酒酵母trm8Δtrm4ΔRTD突变体，由于tRNA ^Val（AAC）衰减，温度敏感性与GAAC激活密切相关；但是，在S中。在酿酒酵母中，GAAC突变会增加tRNA的丢失并加剧温度敏感性。类似的加剧生长缺陷发生时在GAAC突变小号。酿酒酵母trm8Δ和其他触发RTD的单修饰突变体。因此，这些结果证明了保守的GAAC活化与S中的RTD一致。庞贝和小号。酿酒酵母，但在两种生物中GAAC反应的相反影响。我们推测，RTD途径及其对GAAC途径的调控在真核生物中得到了广泛的保守，并延伸至影响tRNA体修饰的其他突变体。