Ribosome Biogenesis Modulates Ty1 Copy Number Control in Saccharomyces cerevisiae
Ribosome Biogenesis Modulates Ty1 Copy Number Control in Saccharomyces cerevisiae
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DOI：
10.1534/genetics.117.300388
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发表时间：
2017-12-01
期刊：
影响因子：
3.3
通讯作者：
Garfinkel, David J.
中科院分区：
文献类型：
--
作者：
Ahn, Hyo Won;Tucker, Jessica M.;Garfinkel, David J.
转座子可以通过改变基因表达和参与染色体重排来影响宿主基因组。因此，生物体进化出不同的方式来最小化转座水平。在酿酒酵母及其近亲奇异酵母中，Ty1 拷贝数控制 (CNC) 由自编码限制因子 p22 介导，该因子源自 GAG 衣壳基因，可抑制病毒样颗粒 (VLP) 的组装和功能。基于 Ty1 辅助因子的二次筛选，我们鉴定了 LOC1，这是一种 RNA 定位/核糖体生物发生基因，主要影响含有 Ty1 元件的菌株中的 Ty1 流动性。核糖体蛋白突变体 rps0b Delta 和 rpl7a Delta 显示出与 loc1 Delta 相似的 CNC 特异性表型，表明核糖体生物发生对于 CNC 至关重要。在这些突变体中，Ty1 mRNA 和编码 p22 的 Ty1 内部 (Ty1i) 转录物的水平发生了改变，并且显示出 Ty1i RNA 水平相对于全长 Ty1 mRNA 增加的趋势。这些突变体中 p22 的水平增加，loc1D 突变体中 p22 的半衰期也增加。转录组分析揭示了 loc1D 突变体中 Ty1 转录物水平或翻译起始效率的微小变化。重要的是，loc1D 突变体在 Gag 复合物的组装和 Ty1 RNA 的包装方面存在缺陷。我们的结果表明，有缺陷的核糖体生物发生通过增加 p22 的水平来增强 CNC，并提高了 VLP 组装、其细胞质环境和新型应激反应之间的多功能联系的可能性。
Transposons can impact the host genome by altering gene expression and participating in chromosome rearrangements. Therefore, organisms evolved different ways to minimize the level of transposition. In Saccharomyces cerevisiae and its close relative S. paradoxus, Ty1 copy number control (CNC) is mediated by the self-encoded restriction factor p22, which is derived from the GAG capsid gene and inhibits virus-like particle (VLP) assembly and function. Based on secondary screens of Ty1 cofactors, we identified LOC1, a RNA localization/ribosome biogenesis gene that affects Ty1 mobility predominantly in strains harboring Ty1 elements. Ribosomal protein mutants rps0b Delta and rpl7a Delta displayed similar CNC-specific phenotypes as loc1 Delta, suggesting that ribosome biogenesis is critical for CNC. The level of Ty1 mRNA and Ty1 internal (Ty1i) transcripts encoding p22 was altered in these mutants, and displayed a trend where the level of Ty1i RNA increased relative to full-length Ty1 mRNA. The level of p22 increased in these mutants, and the half-life of p22 also increased in a loc1D mutant. Transcriptomic analyses revealed small changes in the level of Ty1 transcripts or efficiency of translation initiation in a loc1D mutant. Importantly, a loc1D mutant had defects in assembly of Gag complexes and packaging Ty1 RNA. Our results indicate that defective ribosome biogenesis enhances CNC by increasing the level of p22, and raise the possibility for versatile links between VLP assembly, its cytoplasmic environment, and a novel stress response.