LIN28/let-7 MECHANISMS IN REPROGRAMMING AND METABOLISM

28年前首次报道的线虫异时性突变的遗传筛查， 定义了一条进化保守的途径，控制着生长和发育的全部时间 双边生物，并由此产生了microRNAs的发现。我们发现了一个 两种哺乳动物异时性同源物相关的基本生化机制 蠕虫基因：RNA结合蛋白LIN28抑制let-7 microRNAs的生物发生 (MiRNAs)。我们和其他人已经发现LIN28/LET-7与广泛的生物学有关，包括 哺乳动物生长发育的性成熟时机、体细胞重编程 多能性、生殖细胞发育、癌症、炎症、糖酵解代谢，以及 糖尿病。我们最近的数据将LIN28/let-7轴与糖酵解的转变联系起来 伴随着体细胞重新编程为多能性的代谢。我们还有 LIN28/LET-7与胚胎和多能细胞独特的氨基酸代谢有关，在 苏氨酸/蛋氨酸对S-腺苷甲硫氨酸、组蛋白水平的影响 H3K4甲基化和多能性。哺乳动物中存在线虫祖先LIN28基因 作为两个高度相关的平行曲线A和B，它们显示了不同的时空模式 组织表达，不同的蛋白质结构和修饰，以及不同的RNA靶标。这 提案将分析转录调控、结构/功能关系、后 翻译修饰，以及在上下文中对两个对偶语蛋白质组的影响 体细胞重新编程和新陈代谢，检验LIN28赋予 以胚胎细胞和多能细胞为特征的糖酵解代谢状态。照亮了 LIN28/let-7途径将提供对重新编程的基本见解，同时也 对癌症和糖尿病等疾病过程的了解。了解它的机制注定是 对生物医学具有重大意义。

Genetic screens for heterochronic mutants in C. elegans, first reported twenty-eight years ago, defined an evolutionarily conserved pathway controlling growth and developmental timing in all bilateral organisms, and from which emerged the discovery of microRNAs. We discovered a fundamental biochemical mechanism that relates two mammalian homologues of heterochronic worm genes: the RNA binding protein LIN28 inhibits the biogenesis of let-7 microRNAs (miRNAs). We and others have implicated LIN28/let-7 in a sweeping range of biology including mammalian growth and developmental timing of sexual maturation, somatic cell reprogramming and pluripotency, germ cell development, cancer, inflammation, glycolytic metabolism, and diabetes. Our recent data connects the LIN28/let-7 axis to the shift towards glycolytic metabolism that accompanies reprogramming of somatic cells to pluripotency. We have also linked LIN28/let-7 to the distinctive amino acid metabolism of embryonic and pluripotent cells, in which flux through Threonine/ Methionine influences levels of s-adenosyl methionine, histone H3K4 methylation, and pluripotency. The ancestral C. elegans LIN28 gene exists in mammals as two highly related paralogs, A and B, which show different temporal and spatial patterns of tissue expression, different protein structures and modifications, and different RNA targets. This proposal will analyze transcriptional regulation, structure/function relationships, post- translational modifications, and effects on the proteome of the two paralogs in the context of somatic cell reprogramming and metabolism, testing the hypothesis that LIN28 confers a glycolytic metabolic state characteristic of embryonic and pluripotent cells. Illuminating the LIN28/let-7 pathway will provide fundamental insights into reprogramming while also shedding light on disease processes like cancer and diabetes. Understanding its mechanisms is destined to have major significance for biomedicine.