Hayashi Sachiko, Yoshihisa Tohru
Graduate School of Science, University of Hyogo, Ako-gun, Japan.
PLoS One. 2025 May 30;20(5):e0324525. doi: 10.1371/journal.pone.0324525. eCollection 2025.
In a classical view, each paralogous ribosomal protein (RP) is equally synthesized and integrated into the ribosome. Therefore, RP-paralog mRNAs are generally believed to be similarly regulated on their transcription and/or stability. In this paper, we report that two Rps7p/eS7 paralogs of Saccharomyces cerevisiae are differently regulated; deletion of RPS7A upregulates RPS7B paralogous mRNA expression but not vice versa. Their 3'-UTR sequences critically regulated the stabilities of both RPS7A and RPS7B mRNAs. Alterations in these sequences led to a diminished expression of RPS7A and RPS7B mRNAs in a transcript-dependent manner, suggesting that RPS7-paralog mRNAs have different properties for their expression and/or stability. The C-terminal tagging of the ORF and mutation analyses in the 3'-UTR indicate that both RPS7-paralog mRNAs critically rely on their 3'-UTRs for mRNA expressions and/or stabilities. We also found that activities of both RPS7A and RPS7B promoters are regulated by abundance of Rps7Ap and that Fhl1p, a key transcriptional regulator of RP genes, is essential for transcription of RPS7B but not RPS7A while simultaneous deletion of a consensus sequence for Fhl1p in the RPS7A promoter region and the FHL1 gene completely abolishes the promoter activity. These results indicate that yeast has a distinct buffering system for Rps7p production between the two RPS7-paralogs, which is sensitive to variation on their 3'-UTRs and is partially mediated in a transcription-dependent manner.
在传统观点中，每个旁系同源核糖体蛋白（RP）均以相同的方式合成并整合到核糖体中。因此，人们普遍认为RP旁系同源mRNA在转录和/或稳定性方面受到类似的调控。在本文中，我们报道酿酒酵母的两个Rps7p/eS7旁系同源物受到不同的调控；RPS7A的缺失会上调RPS7B旁系同源mRNA的表达，反之则不然。它们的3'-UTR序列对RPS7A和RPS7B mRNA的稳定性起关键调控作用。这些序列的改变导致RPS7A和RPS7B mRNA的表达以转录本依赖的方式减少，这表明RPS7旁系同源mRNA在表达和/或稳定性方面具有不同的特性。对开放阅读框（ORF）进行C端标记以及在3'-UTR中进行突变分析表明，两个RPS7旁系同源mRNA在mRNA表达和/或稳定性方面都严重依赖其3'-UTR。我们还发现，RPS7A和RPS7B启动子的活性均受Rps7Ap丰度的调控，并且Fhl1p（RP基因的关键转录调节因子）对RPS7B的转录至关重要，但对RPS7A的转录并非如此，而同时缺失RPS7A启动子区域中Fhl1p的共有序列和FHL1基因会完全消除启动子活性。这些结果表明，酵母在两个RPS7旁系同源物之间具有独特的Rps7p产生缓冲系统，该系统对其3'-UTR的变化敏感，并且部分以转录依赖的方式介导。
