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在酿酒酵母氮饥饿期间,自噬和蛋白酶体途径均有助于Ubp3p依赖的翻译和RNA周转因子亚群的消耗。

Both the autophagy and proteasomal pathways facilitate the Ubp3p-dependent depletion of a subset of translation and RNA turnover factors during nitrogen starvation in Saccharomyces cerevisiae.

作者信息

Kelly Shane P, Bedwell David M

机构信息

Department of Cell, Developmental and Integrative Biology, Birmingham, Alabama 35294, USA.

Department of Cell, Developmental and Integrative Biology, Birmingham, Alabama 35294, USA Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.

出版信息

RNA. 2015 May;21(5):898-910. doi: 10.1261/rna.045211.114. Epub 2015 Mar 20.

Abstract

Protein turnover is an important regulatory mechanism that facilitates cellular adaptation to changing environmental conditions. Previous studies have shown that ribosome abundance is reduced during nitrogen starvation by a selective autophagy mechanism termed ribophagy, which is dependent upon the deubiquitinase Ubp3p. In this study, we asked whether the abundance of various translation and RNA turnover factors are reduced following the onset of nitrogen starvation in Saccharomyces cerevisiae. We found distinct differences in the abundance of the proteins tested following nitrogen starvation: (1) The level of some did not change; (2) others were reduced with kinetics similar to ribophagy, and (3) a few proteins were rapidly depleted. Furthermore, different pathways differentially degraded the various proteins upon nitrogen starvation. The translation factors eRF3 and eIF4GI, and the decapping enhancer Pat1p, required an intact autophagy pathway for their depletion. In contrast, the deadenylase subunit Pop2p and the decapping enzyme Dcp2p were rapidly depleted by a proteasome-dependent mechanism. The proteasome-dependent depletion of Dcp2p and Pop2p was also induced by rapamycin, suggesting that the TOR1 pathway influences this pathway. Like ribophagy, depletion of eIF4GI, eRF3, Dcp2p, and Pop2p was dependent upon Ubp3p to varying extents. Together, our results suggest that the autophagy and proteasomal pathways degrade distinct translation and RNA turnover factors in a Ubp3p-dependent manner during nitrogen starvation. While ribophagy is thought to mediate the reutilization of scarce resources during nutrient limitation, our results suggest that the selective degradation of specific proteins could also facilitate a broader reprogramming of the post-transcriptional control of gene expression.

摘要

蛋白质周转是一种重要的调节机制,有助于细胞适应不断变化的环境条件。先前的研究表明,在氮饥饿期间,通过一种称为核糖体自噬的选择性自噬机制,核糖体丰度会降低,这种机制依赖于去泛素化酶Ubp3p。在本研究中,我们探究了酿酒酵母在氮饥饿开始后,各种翻译和RNA周转因子的丰度是否会降低。我们发现氮饥饿后所检测蛋白质的丰度存在明显差异:(1)有些蛋白质的水平没有变化;(2)其他蛋白质的丰度以与核糖体自噬相似的动力学降低,(3)少数蛋白质迅速耗尽。此外,在氮饥饿时,不同的途径以不同方式降解各种蛋白质。翻译因子eRF3和eIF4GI以及脱帽增强子Pat1p的耗尽需要完整的自噬途径。相比之下,去腺苷酸化酶亚基Pop2p和脱帽酶Dcp2p通过蛋白酶体依赖性机制迅速耗尽。雷帕霉素也可诱导蛋白酶体依赖性的Dcp2p和Pop2p的耗尽,这表明TOR1途径影响该途径。与核糖体自噬一样,eIF4GI、eRF3、Dcp2p和Pop2p的耗尽在不同程度上依赖于Ubp3p。总之,我们的结果表明,在氮饥饿期间,自噬和蛋白酶体途径以Ubp3p依赖性方式降解不同的翻译和RNA周转因子。虽然核糖体自噬被认为在营养限制期间介导稀缺资源的再利用,但我们的结果表明,特定蛋白质的选择性降解也可能有助于更广泛地重新编程基因表达的转录后控制。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/45b6/4408797/d619059ddfaa/898F01.jpg

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