Internal ribosome entry sites (IRESs) are functional RNA elements that can directly recruit ribosomes to an internal position of the mRNA in a cap-independent manner to initiate translation. Recently, IRES elements have attracted much attention for their critical roles in various processes including translation initiation of a new type of RNA, circular RNA (circRNA), with no 5′ cap to support classical cap-dependent translation. Thus, an integrative data resource of IRES elements with experimental evidence will be useful for further studies. In this study, we present IRESbase, a comprehensive database of IRESs, by curating the experimentally validated functional minimal IRES elements from literature and annotating their host linear and circular RNAs. The current version of IRESbase contains 1328 IRESs, including 774 eukaryotic IRESs and 554 viral IRESs from 11 eukaryotic organisms and 198 viruses, respectively. As IRESbase collects only IRES of minimal length with functional evidence, the median length of IRESs in IRESbase is 174 nucleotides. By mapping IRESs to human circRNAs and long non-coding RNAs (lncRNAs), 2191 circRNAs and 168 lncRNAs were found to contain at least one entire or partial IRES sequence. IRESbase is available at http://reprod.njmu.edu.cn/cgi-bin/iresbase/index.php.
内部核糖体进入位点（IRES）是一类以非帽依赖方式招募核糖体启动翻译过程的RNA内部功能元件。近来，IRES元件因其在环形RNA（circRNA）翻译起始中的关键性作用引起了人们的广泛关注。circRNA首尾相连，天然缺失帽依赖翻译起始机制所需的5′端帽结构，因此IRES元件对其编码功能至关重要。为促进circRNA的深入研究，我们从文献中手工收集整理了实验验证的IRES元件，建立了一个综合数据库IRESbase，对包含IRES元件的线性及环形RNA进行了详细注释。目前，IRESbase收集了11种真核生物和198种病毒的IRES元件，总共1328个（真核：774，病毒：554）。IRESbase仅收录功能验证的最短IRES元件，库中IRES元件的核苷酸长度中位数为174 nt。此外，基于基因组位置关系，我们发现2191个circRNA和168个lncRNA包含IRES元件或其部分片段。IRESbase访问地址：http://reprod.njmu.edu.cn/cgi-bin/iresbase/index.php。





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