NUCLEAR ENCODED GENES REGULATE CHLOROPLAST TRANSLATION

在单细胞绿色衣藻（Chlamydiumreinhardtii）中鉴定出一组核编码蛋白，其以高特异性和亲和力结合叶绿体编码的psbA mRNA的5 '非翻译区（UTR）。这些蛋白质与5 '-UTR的结合是psbA mRNA翻译所必需的，并且通过升高的ADP水平和氧化还原电位进行调节;这两个生理事件与光合作用有关。代表这些翻译激活因子中的三种的cDNA已经被分离。两个cDNA的序列分析表明，相应的蛋白质代表多聚腺苷酸结合蛋白和蛋白质二硫键异构酶。 此时第三种蛋白质没有指定的功能。 我们已经产生了针对这些蛋白质的抗血清，并分离出两个基因组克隆：基因组文库的筛选应该允许分离第三个克隆。我们计划表征的主要信号和其他组件的信号转导途径，调节每个核编码的psbA结合蛋白基因，以了解它们的表达如何影响翻译的psbA mRNA。这些研究代表了第一个解决克隆的翻译激活因子在植物中的表征，并将提供洞察到的主要信号，调节核编码的翻译激活因子的表达。调节线粒体mRNA翻译的核编码蛋白也已在酵母中鉴定，然而，相应的基因尚未分离。因此，这项研究应该提供重要的洞察到的分子机制（S），信号的表达核编码的翻译激活剂，信息，这将适用于那些系统利用核/细胞器交叉通信。

A set of nuclear-encoded proteins that bind with high specificity and affinity to the 5'-untranslated region (UTR) of the chloroplast- encoded psbA mRNA have been identified in the unicellular green alga Chlamydomonas reinhardtii. Binding of these proteins to 5'-UTR is required for translation of the psbA mRNA and is regulated through elevated ADP levels and redox potential; two physiological events that are linked to photosynthesis. The cDNAs representing three of these translational activators have been isolated. Sequence analysis of two of the cDNAs has revealed that the corresponding proteins represent a poly A binding protein and a protein disulfide isomerase. A third protein at this time has no assigned function. We have produced antisera against these proteins, and have isolated two of the genomic clones: a screen of a genomic library should allow isolation of the third clone. We plan to characterize the primary signal and other components in the signal transduction pathway that regulate each of the nuclear-encoded psbA binding protein genes in order to understand how their expression influences translation of the psbA mRNA. These studies represent the first to address the characterization of cloned translational activators in plants, and will provide insight into the primary signals that regulate the expression of nuclear-encoded translational activators. Nuclear-encoded proteins that regulate the translation of mitochondrial mRNAs have also been identified in yeast, however, the corresponding genes have not been isolated. Therefore, this research should provide important insight into the molecular mechanism(s) that signal the expression of nuclear-encoded translational activators, information which will be applicable to those systems utilizing nuclear/organelle cross-communication.