Modulation of cellular functions by polyamines through polyamine interaction with RNA and proteins

1.在大肠杆菌中，多胺在翻译水平上刺激对细胞生长和活力至关重要的特定蛋白质的合成，如OPPA、CyA和Rpos(σ^&lt；38&gt；)。在这项研究中，我们发现多胺也在翻译水平上刺激Fecl和Fis的合成。Fecl和Fis蛋白促进参与铁吸收和能量代谢的mRNAs以及rRNA和一些tRNAs的表达。当Shine-Dalgarno(SD)序列在这些mRNA上的正常位置被创建时，蛋白质合成不再受到多胺的影响。因此，这些mRNAs的共同特征是具有弱的或无效的SD序列。我们建议将在翻译水平上被多胺增强表达的一组基因称为多胺调节子。2.研究了多胺对大肠杆菌翻译过程中移码的影响。在体内和体外实验系统中，多胺均能刺激RF2mRNA开放阅读框中第26位终止密码子的移码。刺激发生在细胞生长的对数早期，此时RF2mRNA和RF2蛋白的比例较高。通过检测多胺在突触小泡、突触小体和神经胶质细胞中的转运，以及从海马片释放精胺来检测多胺在脑内的循环。研究发现，突触小体和神经胶质细胞中存在膜电位依赖性的多胺转运系统，突触小泡中存在质子梯度依赖性的多胺转运系统。发现精胺在突触小泡中积聚，并通过高浓度KCl去极化从大鼠海马片中释放出来。多胺，特别是精胺，可能在大脑中发挥神经调节剂的作用。

1.Synthesis of specific proteins such as OppA, Cya and RpoS (σ^<38>), which are important for cell growth and viability, is stimulated by polyamines at the level of translation in E. coli. In this study, we found that synthesis of Fecl and Fis was also stimulated by polyamines at the level of translation. Fecl and Fis proteins enhance expression of mRNAs involved in iron uptake and energy metabolism, and of rRNA and some tRNAs. When the Shine-Dalgarno (SD) sequences were created at the normal position on these mRNAs, protein synthesis was no longer influenced by polyamines. Thus, the common characteristic of these mRNAs was to have a weak or ineffective SD sequence. We propose that a group of genes whose expression is enhanced by polyamines at the level of translation is referred to as a "polyamine modulon".2.Effect of polyamines on frameshift during translation in E. coli was studied. Frameshift at the 26th termination codon in the open reading frame of RF2 mRNA was stimulated by polyamines in in vivo and in vitro experimental systems. Stimulation occurred at the early logarithmic phase of cell growth, in which the ratio of RF2 mRNA to RF2 protein is high. Polyamines functioned at the decoding site on ribosomes.3.Cycling of polyamines (spermine and spermidine) in the brain was examined by measuring polyamine transport in synaptic vesicles, synaptosomes and glial cells, and the release of spermine from hippocampal slices. It was found that membrane potential-dependent polyamine transport systems exist in synaptosomes and glial cells, and a proton gradient-dependent polyamine transport system exists in synaptic vesicles. Spermine was found to be accumulated in synaptic vesicles and was released from rat hippocampal slices by depeolarization using a high concentration of KCl. Polyamines, in particular spermine, may function as neuromodulators in the brain.