Arthur David C, Ghetu Alexandru F, Gubbins Michael J, Edwards Ross A, Frost Laura S, Glover J N Mark
Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
EMBO J. 2003 Dec 1;22(23):6346-55. doi: 10.1093/emboj/cdg607.
The protein FinO represses F-plasmid conjugative transfer by facilitating interactions between the mRNA of the major F-plasmid transcriptional activator, TraJ, and an antisense RNA, FinP. FinO is known to bind stem-loop structures in both FinP and traJ RNAs; however, the mechanism by which FinO facilitates sense-antisense pairing is poorly understood. Here we show that FinO acts as an RNA chaperone to promote strand exchange and duplexing between minimal RNA targets derived from FinP. This strongly suggests that FinO may function to destabilize internal secondary structures within FinP and traJ RNAs that would otherwise act as a kinetic trap to sense-antisense pairing. The energy for FinO-catalyzed base-pair destabilization does not arise from ATP hydrolysis but appears to be supplied directly from FinO RNA binding free energy. An analysis of the activities of mutants that are specifically deficient in strand exchange but not RNA-binding activity demonstrates that strand exchange is essential to the ability of FinO to mediate sense-antisense RNA recognition, and that this function also plays a role in repression of conjugation in vivo.
蛋白质FinO通过促进主要F质粒转录激活因子TraJ的mRNA与反义RNA FinP之间的相互作用来抑制F质粒的接合转移。已知FinO能结合FinP和traJ RNA中的茎环结构；然而，FinO促进正义-反义配对的机制却知之甚少。在此我们表明，FinO作为一种RNA伴侣，可促进源自FinP的最小RNA靶标之间的链交换和双链体形成。这有力地表明，FinO可能起到使FinP和traJ RNA内部二级结构不稳定的作用，否则这些二级结构会成为正义-反义配对的动力学陷阱。FinO催化碱基对去稳定化的能量并非来自ATP水解，而是似乎直接由FinO的RNA结合自由能提供。对那些在链交换方面存在特异性缺陷但RNA结合活性正常的突变体活性分析表明，链交换对于FinO介导正义-反义RNA识别的能力至关重要，并且该功能在体内对接合作用的抑制中也发挥作用。
