The Function of RH22, a DEAD RNA Helicase, in the Biogenesis of the 50S Ribosomal Subunits of Arabidopsis Chloroplasts
The Function of RH22, a DEAD RNA Helicase, in the Biogenesis of the 50S Ribosomal Subunits of Arabidopsis Chloroplasts
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RH22（一种 DEAD RNA 解旋酶）在拟南芥叶绿体 50S 核糖体亚基生物发生中的功能
DOI：
10.1104/pp.111.186775
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发表时间：
2012-02-01
期刊：
影响因子：
7.4
通讯作者：
Zhang, Lixin
中科院分区：
文献类型：
--
作者：
Chi, Wei;He, Baoye;Zhang, Lixin
叶绿体核糖体是一种大型动态核糖核蛋白机器，由 30S 和 50S 亚基组成。尽管在过去十年中已经确定了叶绿体核糖体的成分，但驱动叶绿体核糖体生物发生的分子机制仍然很大程度上难以捉摸。在这里，我们证明 RNA 解旋酶 22 (RH22)，一种推定的 DEAD RNA 解旋酶，参与拟南芥 (Arabidopsis thaliana) 的叶绿体核糖体组装。 RH22 的缺失是致命的，而 RH22 表达的敲低会导致绿色幼苗的叶绿体核糖体 RNA (rRNA) 积累出现明显缺陷。 23S 和 4.5S 的前体 rRNA 在 rh22 突变体中积累，但 16S 的前体没有积累。进一步分析表明，RH22 与 50S 核糖体亚基的前体相关。这些结果表明 RH22 可能在叶绿体中 50S 核糖体亚基的组装中发挥作用。此外，RH22 通过酵母双杂交和 Pull-down 测定与 50S 核糖体蛋白 RPL24 相互作用，并且还与包含 RPL24 结合位点的小 23S rRNA 片段结合。 RH22 的这种作用可能与 SrmB（一种参与大肠杆菌核糖体组装的 DEAD RNA 解旋酶）的作用相似但不同，这表明 DEAD RNA 解旋酶和 rRNA 结构可能在核糖体组装和功能方面共同进化。
The chloroplast ribosome is a large and dynamic ribonucleoprotein machine that is composed of the 30S and 50S subunits. Although the components of the chloroplast ribosome have been identified in the last decade, the molecular mechanisms driving chloroplast ribosome biogenesis remain largely elusive. Here, we show that RNA helicase 22 (RH22), a putative DEAD RNA helicase, is involved in chloroplast ribosome assembly in Arabidopsis (Arabidopsis thaliana). A loss of RH22 was lethal, whereas a knockdown of RH22 expression resulted in virescent seedlings with clear defects in chloroplast ribosomal RNA (rRNA) accumulation. The precursors of 23S and 4.5S, but not 16S, rRNA accumulated in rh22 mutants. Further analysis showed that RH22 was associated with the precursors of 50S ribosomal subunits. These results suggest that RH22 may function in the assembly of 50S ribosomal subunits in chloroplasts. In addition, RH22 interacted with the 50S ribosomal protein RPL24 through yeast two-hybrid and pull-down assays, and it was also bound to a small 23S rRNA fragment encompassing RPL24-binding sites. This action of RH22 may be similar to, but distinct from, that of SrmB, a DEAD RNA helicase that is involved in the ribosomal assembly in Escherichia coli, which suggests that DEAD RNA helicases and rRNA structures may have coevolved with respect to ribosomal assembly and function.