The E-coli RhIE RNA helicase regulates the function of related RNA helicases during ribosome assembly
The E-coli RhIE RNA helicase regulates the function of related RNA helicases during ribosome assembly
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DOI：
10.1261/rna.800308
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发表时间：
2008-02-01
期刊：
影响因子：
4.5
通讯作者：
Jain, Chaitanya
中科院分区：
文献类型：
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作者：
Jain, Chaitanya
大肠杆菌含有 DEAD-box RNA 解旋酶家族的五个成员，这是一类普遍存在的蛋白质，其特征在于能够解开 RNA 双链体。尽管其中四种蛋白与 RNA 周转或核糖体生物发生有关，但迄今为止尚未描述过 RhIE DEAD-box 蛋白的细胞功能。在分析缺乏 DeaD/CsdA RNA 解旋酶的菌株的冷敏感生长缺陷时，从染色体文库中鉴定出 rhIE 质粒作为生长缺陷的多拷贝抑制子。值得注意的是，当测试等位基因特异性时，发现 RhIE 过量产生会加剧缺乏 SrmB RNA 解旋酶的菌株的冷敏感生长缺陷。此外，RhIE的缺失分别加剧或减轻了deaD或srmB菌株的冷敏感缺陷。引物延伸和核糖体分析表明，当 deaD 或 srmB 菌株在低温下生长时，RhIE 调节未成熟核糖体 RNA 或核糖体前体的积累。通过使用带有表位标记的 RhIE，发现细胞提取物中的大部分 RhIE 与含核糖体的组分共沉积。由于最近已证明 DeaD 和 SrmB 在核糖体组装中发挥作用，这些发现表明 WE 在遗传上与 srmB 和 deaD 相互作用，以在核糖体成熟过程中调节它们的功能。根据现有证据，我提出 RhIE 是一种新型核糖体组装因子，在核糖体 RNA 折叠中间体的相互转化中发挥作用，这些中间体在核糖体成熟过程中由 DeaD 或 SrmB 进一步加工。
Escherichia coli contains five members of the DEAD-box RNA helicase family, a ubiquitous class of proteins characterized by their ability to unwind RNA duplexes. Although four of these proteins have been implicated in RNA turnover or ribosome biogenesis, no cellular function for the RhIE DEAD-box protein has been described as yet. During an analysis of the cold-sensitive growth defect of a strain lacking the DeaD/CsdA RNA helicase, rhIE plasmids were identified from a chromosomal library as multicopy suppressors of the growth defect. Remarkably, when tested for allele specificity, RhIE overproduction was found to exacerbate the cold-sensitive growth defect of a strain that lacks the SrmB RNA helicase. Moreover, the absence of RhIE exacerbated or alleviated the cold-sensitive defect of deaD or srmB strains, respectively. Primer extension and ribosome analysis indicated that RhIE regulates the accumulation of immature ribosomal RNA or ribosome precursors when deaD or srmB strains are grown at low temperatures. By using an epitope-tagged version of RhIE, the majority of RhIE in cell extracts was found to cosediment with ribosome-containing fractions. Since both DeaD and SrmB have been recently shown to function in ribosome assembly, these findings suggests that WE genetically interacts with srmB and deaD to modulate their function during ribosome maturation. On the basis of the available evidence, I propose that RhIE is a novel ribosome assembly factor, which plays a role in the interconversion of ribosomal RNA-folding intermediates that are further processed by DeaD or SrmB during ribosome maturation.