Ribosome Biogenesis in African Trypanosomes Requires Conserved and Trypanosome-Specific Factors
Ribosome Biogenesis in African Trypanosomes Requires Conserved and Trypanosome-Specific Factors
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DOI：
10.1128/ec.00307-13
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发表时间：
2014-04
期刊：
影响因子：
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通讯作者：
Khan Umaer;Martín Ciganda;N. Williams
中科院分区：
文献类型：
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作者：
Khan Umaer;Martín Ciganda;N. Williams
摘要大核糖体亚基蛋白L5负责5S rRNA的稳定和转运到真核核糖体组装部位。在布氏锥虫中，除了L5，锥虫特异性蛋白P34和P37也参与了这一过程。这两种必需蛋白质通过与核糖体蛋白L5和5S rRNA相互作用形成一种新的胸前颗粒。我们已经建立了一个原环L5 RNA干扰细胞系，并发现L5本身是锥虫生长所必需的蛋白质，尽管存在其他5S rRNA结合蛋白。L5的丢失会降低所有大亚基rRNA、25/28S、5.8S和5S rRNA的水平，但不会改变小亚基18S rRNA的水平。L5的耗尽特别地降低了其他大型核糖体蛋白L3和L11的水平，而这些蛋白的稳定状态下的mRNA水平增加了。L5基因敲除细胞的40S核糖体亚基增加，60S核糖体亚基、80S单体和多聚体丢失。此外，L5还参与了前体rRNA的加工和成熟。对多聚体部分的分析表明，当L5耗尽时，未处理的rRNA中间体在核糖体中积累。虽然我们先前发现P34和P37的缺失不会导致L5水平的变化，但L5的缺失导致P34和P37蛋白的增加，这表明存在一个代偿性反馈环。这项研究表明，核糖体蛋白L5除了具有锥虫特有的非保守特征外，还具有保守的功能，可以作为药物干预的靶点。
ABSTRACT Large ribosomal subunit protein L5 is responsible for the stability and trafficking of 5S rRNA to the site of eukaryotic ribosomal assembly. In Trypanosoma brucei, in addition to L5, trypanosome-specific proteins P34 and P37 also participate in this process. These two essential proteins form a novel preribosomal particle through interactions with both the ribosomal protein L5 and 5S rRNA. We have generated a procyclic L5 RNA interference cell line and found that L5 itself is a protein essential for trypanosome growth, despite the presence of other 5S rRNA binding proteins. Loss of L5 decreases the levels of all large-subunit rRNAs, 25/28S, 5.8S, and 5S rRNAs, but does not alter small-subunit 18S rRNA. Depletion of L5 specifically reduced the levels of the other large ribosomal proteins, L3 and L11, whereas the steady-state levels of the mRNA for these proteins were increased. L5-knockdown cells showed an increase in the 40S ribosomal subunit and a loss of the 60S ribosomal subunits, 80S monosomes, and polysomes. In addition, L5 was involved in the processing and maturation of precursor rRNAs. Analysis of polysomal fractions revealed that unprocessed rRNA intermediates accumulate in the ribosome when L5 is depleted. Although we previously found that the loss of P34 and P37 does not result in a change in the levels of L5, the loss of L5 resulted in an increase of P34 and P37 proteins, suggesting the presence of a compensatory feedback loop. This study demonstrates that ribosomal protein L5 has conserved functions, in addition to nonconserved trypanosome-specific features, which could be targeted for drug intervention.