Nature2014-06-09 4:43 PM

RsmZ—一种喜欢蛋白质的小RNA Structural basis of the non-coding RNA RsmZ acting as a protein sponge 


细菌毒性会涉及由非编码RNAs (如RsmZ)实施的一大转录后调控系统,这些非编码RNAs获取抑制性蛋白(通常为CsrA-型蛋白RsmE),从而释放它们的目标mRNAs,促进翻译激活。利用NMR 和顺磁共振光谱,Frédéric Allain 及同事确定了RsmE 二聚物是怎样在RsmZ上组合形成一个70 kD核糖核蛋白颗粒并防止它发生降解的。他们的数据显示了RsmZ是怎样获取、存储和释放蛋白、充当一个强力蛋白“海绵”的。 


MicroRNA and protein sequestration by non-coding RNAs (ncRNAs) has recently generated much interest. In the bacterial Csr/Rsm system, which is considered to be the most general global post-transcriptional regulatory system responsible for bacterial virulence, ncRNAs such as CsrB or RsmZ activate translation initiation by sequestering homodimeric CsrA-type proteins from the ribosome-binding site of a subset of messenger RNAs. However, the mechanism of ncRNA-mediated protein sequestration is not understood at the molecular level. Here we show for Pseudomonas fluorescens that RsmE protein dimers assemble sequentially, specifically and cooperatively onto the ncRNA RsmZ within a narrow affinity range. This assembly yields two different native ribonucleoprotein structures. Using a powerful combination of nuclear magnetic resonance and electron paramagnetic resonance spectroscopy we elucidate these 70-kilodalton solution structures, thereby revealing the molecular mechanism of the sequestration process and how RsmE binding protects the ncRNA from RNase E degradation. Overall, our findings suggest that RsmZ is well-tuned to sequester, store and release RsmE and therefore can be viewed as an ideal protein ‘sponge’. 






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