Institute of Pharmaceutical Science, King's College London, London, UK.
Faculty of Life Sciences, University of Manchester, Manchester, UK.
Oncogene. 2014 Jan 23;33(4):484-94. doi: 10.1038/onc.2012.604. Epub 2013 Jan 14.
ORAOV1 (oral cancer overexpressed) is overexpressed in many solid tumours, making a key contribution to the development of cancer, but the cellular role of ORAOV1 is unknown. The yeast orthologue of this protein is encoded by the hitherto uncharacterized essential gene, YNL260c. Expression of ORAOV1 restores viability to yeast cells lacking YNL260c. Under nonpermissive conditions, our conditional mutants of YNL260c are defective in the maturation of the 60S ribosomal subunit, whereas maturation of the 40S subunit is unaffected. Also, initiation of translation is abrogated when YNL260c function is lost. YNL260c is indispensible for life in oxygen, but is nonessential under anaerobic conditions. Consequently, the toxic affects of aerobic metabolism on biogenesis and function of the ribosome are alleviated by YNL260c, hence, we rename YNL260c as LTO1; required for biogenesis of the large ribosomal subunit and initiation of translation in oxygen. Lto1 is found in a complex with Rli1/ABCE1, an ATP-binding cassette (ABC)-ATPase bearing N-terminal [4Fe-4S] clusters. Like Lto1, the Rli1/ABCE1 [4Fe-4S] clusters are not required for viability under anaerobic conditions, but are essential in the presence of oxygen. Loss of Lto1 function renders cells susceptible to hydroperoxide pro-oxidants, though this type of sensitivity is specific to certain types of oxidative stress as the lto1 mutants are not sensitive to an agent that oxidizes thiols. These findings reflect a functional interaction between Lto1 and the Rli1/ABCE1 [4Fe-4S] clusters, as part of a complex, which relieves the toxic effects of reactive oxygen species (ROS) on biogenesis and function of the ribosome. This complex also includes Yae1, which bridges the interaction between Lto1 and Rli1/ABCE1. Interactions between members of this complex were demonstrated both in vivo and in vitro. An increased generation of ROS is a feature shared by many cancers. The ORAOV1 complex could prevent ROS-induced ribosomal damage, explaining why overexpression of ORAOV1 is so common in solid tumours.
ORAOV1（口腔癌过表达）在许多实体瘤中过表达，对癌症的发展起着关键作用，但 ORAOV1 的细胞作用尚不清楚。该蛋白的酵母直系同源物由迄今尚未表征的必需基因 YNL260c 编码。ORAOV1 的表达使缺乏 YNL260c 的酵母细胞恢复活力。在非许可条件下，我们的 YNL260c 条件突变体在 60S 核糖体亚基的成熟中存在缺陷，而 40S 亚基的成熟不受影响。此外，当 YNL260c 功能丧失时，翻译的起始被阻断。YNL260c 在氧气中是必不可少的，但在厌氧条件下是非必需的。因此，有氧代谢对核糖体生物发生和功能的毒性影响通过 YNL260c 得到缓解，因此，我们将 YNL260c 重新命名为 LTO1；需要在氧气中进行大核糖体亚基的生物发生和翻译起始。Lto1 与 Rli1/ABCE1 形成复合物，Rli1/ABCE1 是一种带有 N 端 [4Fe-4S] 簇的 ATP 结合盒 (ABC)-ATP 酶。与 Lto1 一样，Rli1/ABCE1 [4Fe-4S] 簇在厌氧条件下不是生存所必需的，但在有氧条件下是必需的。Lto1 功能丧失使细胞容易受到过氧化物促氧化剂的影响，尽管这种类型的敏感性是特定于某些类型的氧化应激的，因为 lto1 突变体对氧化巯基的试剂不敏感。这些发现反映了 Lto1 和 Rli1/ABCE1 [4Fe-4S] 簇之间的功能相互作用，作为复合物的一部分，它缓解了活性氧 (ROS) 对核糖体生物发生和功能的毒性影响。该复合物还包括 Yae1，它桥接了 Lto1 和 Rli1/ABCE1 之间的相互作用。在体内和体外都证明了该复合物成员之间的相互作用。ROS 的大量产生是许多癌症的共同特征。ORAOV1 复合物可以防止 ROS 诱导的核糖体损伤，这解释了为什么 ORAOV1 在实体瘤中如此普遍过表达。
