Morfeldt E, Taylor D, von Gabain A, Arvidson S
Microbiology and Tumorbiology Center, Karolinska Institute, Stockholm, Sweden.
EMBO J. 1995 Sep 15;14(18):4569-77. doi: 10.1002/j.1460-2075.1995.tb00136.x.
The synthesis of virulence factors in Staphylococcus aureus is controlled by a regulatory RNA molecule, RNAIII, encoded by the agr locus. Transcription of genes coding for secreted toxins and enzymes is stimulated, while transcription of cell-surface protein genes is repressed by RNAIII. In the case of staphylococcal alpha-toxin, RNAIII also seems to stimulate translation by an independent mechanism. In this report we show that in a mutant lacking RNAIII the rate of alpha-toxin (hla) production relative to the cellular concentration of hla mRNA was reduced 10-fold as compared with the wild-type strain. A 75% complementarity between the 5' end of RNAIII and the 5' untranslated region of the hla transcript suggests a direct interaction between the RNAs. A complex of RNAIII and hla mRNA was demonstrated in extracts of total RNA from the wild-type strain, and also with in vitro synthesized RNAs. Ribonuclease T1 digestion experiments revealed that the ribosome binding site of the hla transcript is blocked by intramolecular base-pairing. Hybridization with RNAIII prevents this intramolecular base-pairing and makes the hla mRNA accessible for translation initiation. This is, to our knowledge, the first example of an 'antisense RNA' that stimulates translation of the target mRNA.
金黄色葡萄球菌中致病因子的合成受一种由agr基因座编码的调控RNA分子RNAIII控制。编码分泌毒素和酶的基因转录受到刺激，而细胞表面蛋白基因的转录则被RNAIII抑制。就葡萄球菌α毒素而言，RNAIII似乎还通过一种独立机制刺激翻译。在本报告中，我们表明，与野生型菌株相比，在缺乏RNAIII的突变体中，α毒素（hla）的产生速率相对于hla mRNA的细胞浓度降低了10倍。RNAIII的5'端与hla转录本的5'非翻译区之间75%的互补性表明RNA之间存在直接相互作用。在野生型菌株的总RNA提取物中以及体外合成的RNA中都证实了RNAIII与hla mRNA的复合物。核糖核酸酶T1消化实验表明，hla转录本的核糖体结合位点被分子内碱基配对阻断。与RNAIII杂交可防止这种分子内碱基配对，并使hla mRNA能够进行翻译起始。据我们所知，这是“反义RNA”刺激靶mRNA翻译的首个例子。
