Iadevaia Valentina, Caldarola Sara, Tino Elisa, Amaldi Francesco, Loreni Fabrizio
Department of Biology, University of Rome Tor Vergata, 00133 Rome, Italy,
RNA. 2008 Sep;14(9):1730-6. doi: 10.1261/rna.1037108. Epub 2008 Jul 24.
Terminal oligopyrimidine (TOP) mRNAs (encoded by the TOP genes) are identified by a sequence of 6-12 pyrimidines at the 5' end and by a growth-associated translational regulation. All vertebrate genes for the 80 ribosomal proteins and some other genes involved, directly or indirectly, in translation, are TOP genes. Among the numerous translation factors, only eEF1A and eEF2 are known to be encoded by TOP genes, most of the others having not been analyzed. Here, we report a systematic analysis of the human genes for translation factors. Our results show that: (1) all five elongation factors are encoded by TOP genes; and (2) among the initiation and termination factors analyzed, only eIF3e, eIF3f, and eIF3h exhibit the characteristics of TOP genes. Interestingly, these three polypeptides have been recently shown to constitute a specific subgroup among eIF3 subunits. In fact, eIF3e, eIF3f, and eIF3h are the part of the functional core of eIF3 that is not conserved in Saccharomyces cerevisiae. It has been hypothesized that they are regulatory subunits, and the fact that they are encoded by TOP genes may be relevant for their function.
末端寡嘧啶（TOP）mRNA（由TOP基因编码）通过5'端6至12个嘧啶序列以及与生长相关的翻译调控来识别。所有脊椎动物的80种核糖体蛋白基因以及其他一些直接或间接参与翻译的基因都是TOP基因。在众多翻译因子中，已知只有eEF1A和eEF2由TOP基因编码，其他大多数尚未进行分析。在此，我们报告了对人类翻译因子基因的系统分析。我们的结果表明：（1）所有五个延伸因子均由TOP基因编码；（2）在分析的起始和终止因子中，只有eIF3e、eIF3f和eIF3h表现出TOP基因的特征。有趣的是，最近已证明这三种多肽在eIF3亚基中构成一个特定亚组。实际上，eIF3e、eIF3f和eIF3h是eIF3功能核心的一部分，而该部分在酿酒酵母中并不保守。据推测，它们是调节亚基，并且它们由TOP基因编码这一事实可能与其功能相关。
