Utp14 interaction with the Small Subunit Processome.

The SSU Processome (sometimes referred to as 90S) is an early stable intermediate in the small ribosomal subunit biogenesis pathway of eukaryotes. Progression of the SSU Processome to a pre-40S particle requires a large-scale compaction of the RNA and release of many biogenesis factors. The U3 snoRNA is a primary component of the SSU Processome and hybridizes to the rRNA at multiple locations to organize the structure of the SSU Processome. Thus, release of U3 is prerequisite for the transition to pre-40S. Our lab proposed that the RNA helicase Dhr1 plays a crucial role in the transition by unwinding U3 and that this activity is controlled by the SSU Processome protein Utp14. How Utp14 times the activation of Dhr1 is an open question. Despite being highly conserved, Utp14 contains no recognizable domains, and how Utp14 interacts with the SSU Processome is not well characterized. Here, we used UV crosslinking and analysis of cDNA (CRAC) and yeast two-hybrid interaction to characterize how Utp14 interacts with the pre-ribosome. Moreover, proteomic analysis of SSU particles lacking Utp14 revealed that the presence of Utp14 is needed for efficient recruitment of the RNA exosome. Our analysis positions Utp14 to be uniquely poised to communicate the status of assembly of the SSU Processome to Dhr1 and possibly to the exosome as well.SSU加工体（SSU Processome，有时也被称为90S颗粒）是真核生物小核糖体亚基生物发生通路中的早期稳定中间产物。SSU加工体向pre-40S颗粒（pre-40S particle）转变需要经历RNA的大规模折叠压缩，并释放多种生物发生因子。U3小核仁RNA（U3 snoRNA）是SSU加工体的核心组分，可在多个位点与核糖体RNA（rRNA）杂交，以构建SSU加工体的结构。因此，U3的释放是向pre-40S颗粒转变的先决条件。本课题组提出，RNA解旋酶Dhr1通过解旋U3 snoRNA在该转变过程中发挥关键作用，且该活性受SSU加工体蛋白Utp14调控。Utp14如何调控Dhr1的激活时机仍是一个未解决的科学问题。尽管Utp14高度保守，但未发现可识别的结构域，目前对Utp14与SSU加工体的相互作用机制尚不清楚。本研究采用紫外线交联与cDNA分析（CRAC）及酵母双杂交实验，解析Utp14与核糖体前体的相互作用机制。此外，通过对缺失Utp14的SSU颗粒进行蛋白质组学分析，发现Utp14的存在对于RNA外切体（RNA exosome）的高效招募至关重要。本研究分析表明，Utp14处于独特且适宜的位置，能够向Dhr1传递SSU加工体的组装状态信息，同时也可能将此类信号传递给RNA外切体。