van Biesen T, Frost L S
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
Mol Microbiol. 1994 Nov;14(3):427-36. doi: 10.1111/j.1365-2958.1994.tb02177.x.
Most of the genes required for the conjugative transfer of DNA are encoded by the 33 kb transfer (tra) operon of F-like conjugative plasmids. Transcription of the tra operon is positively regulated by the TraJ transcriptional activator which, in turn, is negatively regulated by the FinOP fertility inhibition system. The FinOP system consists of an antisense RNA, FinP, and a 21.2 kDa protein, FinO, which together inhibit TraJ expression. Previously, it has been demonstrated that FinO increases the in vivo stability of the FinP RNA in the absence of the traJ mRNA target. Using electrophoretic mobility shift assays, we have shown that FinO is an RNA-binding protein that binds to one of the two stem-loops in FinP and to its complementary structure in traJ mRNA. This interaction presumably protects FinP RNA from degradation in vivo and increases the rate of formation of the FinP-traJ mRNA duplex fivefold. Thus, TraJ expression appears to be influenced by a unique RNA-protein interaction that precedes duplex formation between the FinP antisense RNA and its target traJ mRNA.
DNA接合转移所需的大多数基因由F样接合质粒的33 kb转移（tra）操纵子编码。tra操纵子的转录受TraJ转录激活因子的正向调控，而TraJ转录激活因子又受FinOP育性抑制系统的负向调控。FinOP系统由反义RNA FinP和21.2 kDa的蛋白质FinO组成，它们共同抑制TraJ的表达。此前已证明，在没有traJ mRNA靶标的情况下，FinO可提高FinP RNA在体内的稳定性。通过电泳迁移率变动分析，我们表明FinO是一种RNA结合蛋白，它与FinP中的两个茎环之一及其在traJ mRNA中的互补结构结合。这种相互作用可能保护FinP RNA在体内不被降解，并使FinP-traJ mRNA双链体的形成速率提高五倍。因此，TraJ的表达似乎受到一种独特的RNA-蛋白质相互作用的影响，这种相互作用先于FinP反义RNA与其靶标traJ mRNA之间的双链体形成。
