Splicing-Mediated Autoregulation Modulates Rpl22p Expression in Saccharomyces cerevisiae.
Splicing-Mediated Autoregulation Modulates Rpl22p Expression in Saccharomyces cerevisiae.
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DOI：
10.1371/journal.pgen.1005999
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发表时间：
2016-04
期刊：
影响因子：
4.5
通讯作者：
Chanfreau G
中科院分区：
文献类型：
--
作者：
Gabunilas J;Chanfreau G
在酿酒酵母中，剪接对于核糖体蛋白基因（RPGs）的表达至关重要，RPGs是最高表达的基因之一，并且根据生长和环境条件受到严格调控。然而，RPG前mRNA剪接的精确机制的知识是缺乏基因的基因基础上进行调节。在这里，我们表明Rpl22 p在抑制RPL22 B前mRNA转录物的剪接中具有核糖体外作用。内含子内的茎环二级结构对于Rpl22p在体内的前体mRNA结合以及在体内和体外的剪接抑制是必需的，并且当以反式添加到剪接反应中时可以在体外挽救剪接抑制。Rpl22p的剪接抑制可能部分归因于在RPL22B基因座处共转录的U1 snRNP募集到前mRNA的减少。我们进一步证明，RPL22 B前mRNA剪接的抑制有助于在特定的应激条件下成熟转录物的下调，并提供证据暗示在抑制核糖体生物合成的条件下，这种机制的调节作用。这些结果证明了一种自动调节机制，该机制根据核糖体生物发生的细胞需求微调Rp122蛋白的表达，并扩展为Rp122 p旁系同源物组成。核糖体负责所有活细胞中的蛋白质生产，作为遗传信息从RNA翻译为蛋白质的基础。鉴于核糖体在蛋白质组装中的重要作用，核糖体组分高度表达并受到严格调控。还已知一些核糖体蛋白参与核糖体外活性。在我们的研究中，我们证明了核糖体蛋白Rpl22p能够通过抑制其自身RNA转录物的加工来调节其自身的表达，从而导致RNA的降解。我们还表明，这种自我施加的调节在特定的应激条件下限制RPL 22转录水平发挥作用。我们认为，这种机制可能会影响核糖体的组成，通过影响Rpl22p旁系同源物的可用性。
In Saccharomyces cerevisiae, splicing is critical for expression of ribosomal protein genes (RPGs), which are among the most highly expressed genes and are tightly regulated according to growth and environmental conditions. However, knowledge of the precise mechanisms by which RPG pre-mRNA splicing is regulated on a gene-by-gene basis is lacking. Here we show that Rpl22p has an extraribosomal role in the inhibition of splicing of the RPL22B pre-mRNA transcript. A stem loop secondary structure within the intron is necessary for pre-mRNA binding by Rpl22p in vivo and splicing inhibition in vivo and in vitro and can rescue splicing inhibition in vitro when added in trans to splicing reactions. Splicing inhibition by Rpl22p may be partly attributed to the reduction of co-transcriptional U1 snRNP recruitment to the pre-mRNA at the RPL22B locus. We further demonstrate that the inhibition of RPL22B pre-mRNA splicing contributes to the down-regulation of mature transcript during specific stress conditions, and provide evidence hinting at a regulatory role for this mechanism in conditions of suppressed ribosome biogenesis. These results demonstrate an autoregulatory mechanism that fine-tunes the expression of the Rpl22 protein and by extension Rpl22p paralog composition according to the cellular demands for ribosome biogenesis. Ribosomes are responsible for protein production in all living cells, serving as the grounds for the translation of genetic information from RNA to protein. Given the vital role of the ribosome in protein assembly, ribosome components are highly expressed and are subject to tight regulation. Some ribosomal proteins are also known to engage in extra-ribosomal activities. In our study, we demonstrate that the ribosomal protein Rpl22p is able to regulate its own expression by inhibiting the processing of its own RNA transcript, leading to degradation of the RNA. We also show that this self-imposed regulation plays a role in limiting RPL22 transcript levels in specific stress conditions. We suggest that this mechanism may impact the composition of ribosomes by influencing the availability of the Rpl22p paralogs.