Internal ribosome entry sites (IRESs) can be found in the mRNA of many viruses as well as in cellular genes involved in the stress response, cell cycle, and apoptosis. IRES-mediated translation can occur when dominant cap-dependent translation is inhibited, and viruses can take advantage of this to subvert host translation machinery. In this review, we focus on the four major types of IRES identified in RNA viruses, and outline their distinct structural properties and requirements of translational factors. We further discuss auxiliary host factors known as IRES trans-acting factors (ITAFs), which are involved in the modulation of optimal IRES activity. Currently known strategies employed by viruses to harness ITAFs and regulate IRES activity are also highlighted.

内部核糖体进入位点（IRESs）可以在许多病毒的mRNA中以及在应激反应，细胞周期和细胞凋亡中涉及的细胞基因中找到。当显性帽依赖性翻译受到抑制时，IRES介导的翻译就可能发生，病毒可以利用这种优势来颠覆宿主翻译机制。在这篇综述中，我们重点介绍在RNA病毒中鉴定出的IRES的四种主要类型，并概述其独特的结构特性和翻译因子的要求。我们进一步讨论称为IRES反式作用因子（ITAF）的辅助宿主因子，其参与最佳IRES活性的调节。还着重介绍了病毒利用其利用ITAF和调节IRES活性的当前已知策略。