Translational control of msl-2 mRNA: unravelling a new uORF function

性致死（SXL）与5'和3' UTR位点结合介导的msl-2 mRNA的翻译抑制对于雌性果蝇的剂量补偿和生存非常重要。在此之前，我们建立了一个果蝇胚胎体外系统，忠实地再现了这种翻译反应。我们发现SXL通过5' UTR结合位点干扰核糖体扫描，而SXL和辅阻遏蛋白UNR与3' UTR的结合抑制43 S募集。在当前的资助周期中，我们证明了3 'UTR控制涉及poly（A）-尾和PABP。由于“闭环”的形成仍然发生在被抑制的mRNA上，我们确定了一种新的翻译控制机制。我们现在建议将重点放在5 'UTR介导的核糖体扫描的SXL调节机制。初步数据表明，这种机制需要一个上游开放阅读框架（uORF），和SXL增强抑制作用的uORF的未知机制。我们将剖析这种新的模式的RNA结合蛋白调节uORF功能的机制，并探讨这种机制的范围内的调节转录组。

Translational repression of msl-2 mRNA mediated by binding of sex lethal (SXL) to sites in both the 5’ and 3’ UTR is important in female flies for dosage compensation and survival. Previously, we estab-lished a Drosophila embryo in vitro system that faithfully recapitulates this translational response. We showed that SXL interferes with ribosomal scanning via the 5’ UTR binding site, while association of SXL and the corepressor protein UNR with the 3’ UTR inhibits 43S recruitment. During the current funding cycle we demonstrated that 3’UTR control involves the poly(A)-tail and PABP. Since ‘closed-loop’ formation still occurs on the repressed mRNA, we identified a novel mechanism of translational control. We now propose to focus on the mechanism of 5’UTR-mediated regulation of ribosomal scanning by SXL. Preliminary data have shown that this mechanism requires an upstream open reading frame (uORF), and that SXL augments the repressive effect of the uORF by an unknown mechanism. We will dissect this new paradigm of RNA-binding protein-regulated uORF function mechanistically, and explore the scope of this mechanism in the regulation of the transcriptome.