Key message

tRNA Adenosine Deaminase 3 helps to sustain telomere tracts in a telomerase-independent fashion, likely through regulating cellular metabolism.

Abstract

Telomere length maintenance is influenced by a complex web of chromatin and metabolism-related factors. We previously reported that a lncRNA termed AtTER2 regulates telomerase activity in Arabidopsis thaliana in response to DNA damage. AtTER2 was initially shown to partially overlap with the 5′ UTR of the tRNA ADENOSINE DEAMINASE 3 (TAD3) gene. However, updated genome annotation showed that AtTER2 was completely embedded in TAD3, raising the possibility that phenotypes ascribed to AtTER2 could be derived from TAD3. Here we show through strand-specific RNA-Seq, strand-specific qRT-PCR and bioinformatic analyses that AtTER2 does not encode a stable lncRNA. Further examination of the original tad3 (ter2-1/tad3-1) mutant revealed expression of an antisense transcript driven by a cryptic promoter in the T-DNA. Hence, a new hypomorphic allele of TAD3 (tad3-2) was examined. tad3-2 mutants showed hypersensitivity to DNA damage, but no deregulation of telomerase, suggesting that the telomerase phenotype of tad3-1 mutants reflects an off-target effect. Unexpectedly, however, tad3-2 plants displayed progressive loss of telomeric DNA over successive generations that was not accompanied by alteration of terminal architecture or end protection. The phenotype was exacerbated in plants lacking the telomerase processivity factor POT1a, indicating that TAD3 promotes telomere maintenance through a non-canonical, telomerase-independent pathway. The transcriptome of tad3-2 mutants revealed significant dysregulation of genes involved in auxin signaling and glucosinolate biosynthesis, pathways that intersect the stress response, cell cycle regulation and DNA metabolism. These findings indicate that the TAD3 locus indirectly contributes to telomere length homeostasis by altering the metabolic profile in Arabidopsis.

中文翻译：

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tRNA 腺苷脱氨酶 3 是拟南芥中端粒维持所必需的。

关键信息

tRNA 腺苷脱氨酶 3 有助于以不依赖端粒酶的方式维持端粒束，这可能是通过调节细胞代谢。

抽象的

端粒长度的维持受到染色质和代谢相关因素的复杂网络的影响。我们之前报道过一种称为AtTER2 的 lncRNA调节拟南芥中的端粒酶活性以响应 DNA 损伤。AtTER2最初显示与tRNA 腺苷脱氨酶 3 ( TAD3 ) 基因的 5' UTR 部分重叠。然而，更新的基因组注释显示AtTER2完全嵌入TAD3 中，这增加了归因于AtTER2 的表型可能源自TAD3 的可能性. 在这里，我们通过链特异性 RNA-Seq、链特异性 qRT-PCR 和生物信息学分析表明AtTER2不编码稳定的 lncRNA。对原始tad3 ( ter2-1/tad3-1 ) 突变体的进一步检查揭示了由 T-DNA 中的隐蔽启动子驱动的反义转录物的表达。因此，检查了TAD3 的新亚形等位基因(tad3-2 )。tad3-2突变体对 DNA 损伤表现出超敏反应，但端粒酶没有失调，表明tad3-1突变体的端粒酶表型反映了脱靶效应。然而没想到，tad3-2植物在连续几代中表现出端粒 DNA 的逐渐丧失，但不伴随末端结构或末端保护的改变。该表型在缺乏端粒酶持续合成因子POT1a 的植物中加剧，表明TAD3通过非规范的、不依赖端粒酶的途径促进端粒维持。tad3-2突变体的转录组揭示了涉及生长素信号传导和芥子油苷生物合成的基因的显着失调，这些通路与应激反应、细胞周期调节和 DNA 代谢相交。这些发现表明，TAD3基因座通过改变体内的代谢特征间接促进端粒长度的稳态。拟南芥。