van Biesen T, Söderbom F, Wagner E G, Frost L S
Department of Microbiology, University of Alberta, Edmonton, Canada.
Mol Microbiol. 1993 Oct;10(1):35-43. doi: 10.1111/j.1365-2958.1993.tb00901.x.
The efficiency of conjugation of F-like plasmids is regulated by the FinOP fertility inhibition system. The transfer (tra) operon is under the direct control of the TraJ transcriptional activator which, in turn, is negatively regulated by FinP, an antisense RNA, and FinO, a 22 kDa protein. Recently, FinO has been shown to extend the chemical stability of FinP in vivo in the absence of traJ mRNA. The in vitro secondary structures of both the FinP and TraJ RNAs were determined by the use of single- and double-strand-specific nucleases; both RNAs were found to have double stem-loop structures that are complementary to each other and, therefore, FinP RNA and TraJ RNA have the potential to form a duplex with each other. This was verified by in vitro binding experiments. The reaction was shown to be biomolecular with an apparent rate constant (kapp) of 5 x 10(5)M-1s-1, a value that is similar to those found for other natural antisense RNA systems. Preliminary evidence for the in vivo formation of the FinP-TraJ RNA duplex was obtained by primer extension of the traJ mRNA; the presence of both FinO and FinP was required to cause a dramatic reduction in the steady-state level of traJ mRNA, perhaps as a result of RNase III degradation of the resulting RNA duplex.
F 类质粒的接合效率受 FinOP 育性抑制系统调控。转移（tra）操纵子受 TraJ 转录激活因子的直接控制，而 TraJ 又受到反义 RNA FinP 和 22 kDa 蛋白 FinO 的负调控。最近研究表明，在缺乏 traJ mRNA 的情况下，FinO 可在体内延长 FinP 的化学稳定性。通过使用单链和双链特异性核酸酶确定了 FinP 和 TraJ RNA 的体外二级结构；发现这两种 RNA 均具有相互互补的双茎环结构，因此，FinP RNA 和 TraJ RNA 有可能相互形成双链体。体外结合实验证实了这一点。该反应显示为双分子反应，表观速率常数（kapp）为 5×10⁵ M⁻¹s⁻¹，该值与其他天然反义 RNA 系统的值相似。通过对 traJ mRNA 进行引物延伸获得了 FinP - TraJ RNA 双链体在体内形成的初步证据；FinO 和 FinP 的存在均是导致 traJ mRNA 稳态水平显著降低所必需的，这可能是由于 RNase III 对所得 RNA 双链体的降解所致。
