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

 描述(由申请人提供)：核糖体生物发生是任何生长或代谢活跃的细胞的基本和能量密集型过程。完全失去这一过程与生活格格不入。然而，核糖体生物发生缺陷与包括癌症和发育疾病在内的一系列疾病有关，这些疾病被称为核糖体疾病。一种推测为肝脏特异性缺陷的核糖体病是北美印第安儿童肝硬变(NAIC)，其特征是一过性新生儿黄疸进展为胆汁性肝硬变。唯一有效的治疗方法是肝移植。这种疾病的患者在人类UTP4/Cirhin(hUTP4/Cirhin)的C-末端区域有R565W突变，hUTP4/Cirhin是SSU过程组t-UTP/UTPA亚复合体的成员，这两个亚复合体都是前rRNA转录和处理所必需的。我们的实验室先前已经证明hUTP4/Cirhin的C末端与一种新的后生动物特异性核糖体生物发生因子NOL11相互作用。R565W突变破坏了hUTP4/Cirhin与NOL11之间的相互作用，使我们推测NAIC的发病机制是由于核仁功能障碍。具体目的：第一个目的是检验前rRNA处理缺陷导致NAIC发病的假设。我将检测R565W突变对细胞培养中人类前rRNA加工的影响，并测试R565W突变对t-UTP/UTPA亚复合体和SSU过程组内蛋白质-蛋白质相互作用的影响。由于对所有t-UTP/UTPA亚复合体成员的完整了解对于剖析NAIC的发病机制是必要的，我建议发现酵母Utp9的最终未知的人类t-UTP/UTPA亚复合体类似物。核仁应激反应与许多其他核糖病有关。因此，我将检验R565W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，我将建立热带非洲爪鼠作为该疾病的模型，以便在发育中的有机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.