Probing the Pathogenesis of North American Indian Childhood Cirrhosis (NAIC)

 描述（由申请人提供）：核糖体生物合成是任何生长或代谢活性细胞的基本和能量密集型过程。完全失去这一过程是与生命不相容的。然而，核糖体生物合成的缺陷与一系列疾病有关，包括癌症和发育疾病，称为核糖体病。一种假定的伴有肝脏特异性缺陷的核糖体病是北美印第安儿童肝硬化（NAIC），其特征是短暂的新生儿黄疸进展为胆汁性肝硬化。唯一有效的治疗方法是肝移植。患有这种疾病的患者在人UTP 4/Cirhin（hUTP 4/Cirhin）的C-末端区域中具有R565 W突变，所述人UTP 4/Cirhin是SSU加工体的t-UTP/UTPA亚复合物的成员，两者都是前rRNA转录和加工所需的。我们的实验室先前已经表明，hUTP 4/Cirhin的C-末端与一种新的后生动物特异性核糖体生物合成因子NOL 11相互作用。R565 W突变破坏了hUTP 4/Cirhin和NOL 11之间的相互作用，使我们假设NAIC的发病机制是由于核仁功能障碍。具体目的：第一个目的是检验有缺陷的前rRNA加工有助于NAIC发病机制的假设。我将检查R565 W突变对细胞培养中人前rRNA加工的影响，并测试R565 W突变对t-UTP/UTPA亚复合物和SSU加工体中蛋白质-蛋白质相互作用的影响。作为一个完整的了解所有的t-UTP/UTPA亚复合物的成员是必要的解剖NAIC的发病机制，我建议发现最终身份不明的人的t-UTP/UTPA亚复合物类似物的酵母Utp 9。核仁应激反应与许多其他核糖体病有关。因此，我将检验R565 W突变导致p53诱导的假设。由于NAIC是一种先天性疾病，在第二个目标中，我将建立热带爪蟾作为该疾病的模型，允许在发育中的生物体的背景下研究其发病机制。

 DESCRIPTION (provided by applicant): Ribosome biogenesis is a fundamental and energy intensive process for any growing or metabolically active cells. Complete loss of this process is incompatible with life. However, defects in ribosome biogenesis have been associated with a range of maladies including cancer and developmental diseases, termed ribosomopathies. One putative ribosomopathy with liver-specific defects is North American Indian Childhood Cirrhosis (NAIC), characterized by transient neonatal jaundice progressing to biliary cirrhosis. The only effective treatment is liver transplantation. Patients with this disease have an R565W mutation in the C-terminal region of human UTP4/Cirhin (hUTP4/Cirhin), a member of the t-UTP/UTPA subcomplex of the SSU processome, both of which are required for pre-rRNA transcription and processing. Our laboratory has previously shown that the C-terminus of hUTP4/Cirhin interacts with a novel, metazoan- specific ribosome biogenesis factor called NOL11. The R565W mutation disrupts the interaction between hUTP4/Cirhin and NOL11 leading us to hypothesize that the pathogenesis of NAIC is due to nucleolar dysfunction. SPECIFIC AIMS: The first aim will test the hypothesis that defective pre-rRNA processing contributes to the pathogenesis of NAIC. I will examine the effects of the R565W mutation on human pre- rRNA processing in cell culture and test the effect of the R565W mutation on protein-protein interactions within the t-UTP/UTPA subcomplex and SSU processome. As a complete understanding of all the t-UTP/UTPA subcomplex members is necessary for dissecting the pathogenesis of NAIC, I propose to discover the final unidentified human t-UTP/UTPA subcomplex analog of yeast Utp9. The nucleolar stress response is implicated in many other ribosomopathies. Therefore, I will test the hypothesis that the R565W mutation results in p53 induction. Since NAIC is a congenital disease, in the second aim I will establish Xenopus tropicalis as a model for the disease, allowing for the study of its pathogenesis within the context of a developing organism.