Molecular mechanism of antizyme frameshifting

1. 抗酶mRNA上的两个序列元件，移码位点下游的假结结构和上游的富含gc的区域，在无细胞和动物细胞培养系统中都被证实是移码的刺激信号。上游元件被证明与延长核糖体相互作用。这些顺式作用元件也提高了其他移码事件的效率，如病毒- 1移码。然而，多胺的激框效应不是由顺式作用元件与多胺相互作用介导的。大肠杆菌释放因子2 （RE2）信号上的+1移帧和病毒信号上的终止密码子读通等终止密码子的编码现象也被多胺增强。实验结果不支持多胺抑制终止过程的可能性。移码刺激的多胺相互作用位点有待于将来确定。对稳定表达该报告结构的转染动物细胞的移码效率和多胺含量的分析表明，未结合的多胺是刺激细胞内抗酶移码的主要原因。发现了一些刺激或抑制抗酶移框的化合物。Agmatine是一种刺激物质，Agmatine通过消耗细胞多胺而表现出抗增殖作用。二胺衍生物抑制了与多胺竞争时的帧移，可作为分子探针用于寻找多胺相互作用位点。分离了鸡和斑马鱼的抗酶cdna。新的抗酶异构体的替代功能也被发现。这些结果表明，抗酶及其移框在系统发育上具有悠久的历史和广泛的分布。分裂酵母（Schizosaccharomyces pombe）被证明是一种适合的模式生物，用于遗传筛选参与抗酶移框的反式作用因子。在s.p.o pombe中建立多胺依赖的抗酶移框分析系统正在进行中。少

1. Two sequence elements on antizyme mRNA, a pseudoknot structure downstream to and a GC-rich region upstream to the frameshift site, were confirmed to be stimulatory signals for the frameshifting both in cell-free and animal cell culture systems. The upstream element was shown to interact with elongating ribosomes. These cis-acting elements also increased the efficiencies of other frameshift events such as viral -l frameshifting. However, the frameshiftstimulating effect of polyamines was not mediated by interaction between the cis-acting elements and polyamines. Certain recoding phenomena at the terminator codons such as +1 frameshifting on E.coli release factor 2 (RE2) signal and stop codon readthrough on viral signals were also enhanced by polyamines. The possibility that polyamines repress the termination process was not supported by experimental results. The polyamine-interacting site(s)for frameshift stimulation is to be determined in the future.2. Analysis of frameshift efficie … More ncy and polyamine contents in transfected mammalian cells which stably express the reporter construct revealed that the unbound polyamines are responsible for the stimulation of antizyme frameshifting in the cells.3. Some compounds which either stimulate or inhibit antizyme frameshifting were found.Agmatine was one of the stimulatory substances, agmatine and showed anti-proliferative effect through depletion of the cellular polyamines. Diamine derivatives which inhibit the frameshifting in competition with polyamines will be useful as molecular probes to search the polyamine-interacting site(s).4. Antizyme cDNAs of chicken and zebrafish were isolated. Alternative functions of new antizyme isoforms were also found. These results revealed that antizyme and its frameshifting are phylogenetically old and widely distribute.5. A fission yeast, Schizosaccharomyces pombe, was shown to be a suitable model organism for genetic screening of trans-acting factors involved in antizyme frameshifting. Construction of an assay system for polyamine-dependent antizyme frameshifting in S.pombe is underway. Less