The Function of Tribbles in the Pathogenesis of AML

Tribbles蛋白是已知的三种哺乳动物同源蛋白，是一种与蛋白质降解有关的特征较差的蛋白质。它们的特点是中心无功能激酶样结构域。我们最近发现Tribbles同源物2 （Trib2）是生长停滞的白血病细胞中notch调控的转录物。为了研究Trib2在体内的功能，我们用逆转录表达Trib2的造血干细胞重组小鼠。所有重组Trib2的小鼠均可发生克隆性急性髓性白血病（AML），并可连续转移。由于果蝇Tribbles负调控C/EBP的同系物slbo，我们研究了Trib2与C/EBP的关系。我们在C/EBPa复合物中发现了Trib2，导致C/EBPa降解。为了确定我们的发现与人类AML的相关性，对人类AMI患者样本中Trib2 mRNA表达的调查发现，在一部分样本中Trib2表达升高。总之，我们的数据确定Trib2是AML发病机制中的一个致癌基因，通过灭活C/EBPa发挥作用。本研究的目标是确定Trib2诱导C/EBPa降解的机制，确定Trib2诱导AML的机制，鉴定表达Trib2的启动AML的造血祖细胞，以及鉴定在AML发病机制中与Trib2合作的基因。这些研究不仅有助于更好地了解AML的发病机制，而且具有直接的转化效用，因为它们将确定诊断和治疗AML的新靶点。本项目中描述的实验将从与其他项目负责人及其项目的广泛互动中受益匪浅，并将广泛使用科学核心。

Tribbles proteins, of which three mammalian homologues are known, are poorly characterized proteins that have been implicated in protein degradation. They are characterized by a central non-functional kinase-like domain. We recently identified Tribbles homologue 2 (Trib2) as a Notch-regulated transcript in leukemic cells undergoing growth arrest. To investigate the in vivo function of Trib2, mice were reconstituted with hematopoietic stem cells retrovirally expressing Trib2. All Trib2 reconstituted mice developed clonal acute myelogenous leukemia (AML) that could be serially transferred. Because Drosophila Tribbles negatively regulates slbo, the Drosophila homologue of C/EBP, we investigated the relationship between Trib2 and C/EBPa. We identified Trib2 in a complex with C/EBPa, which resulted in C/EBPa degradation. To determine the relevance of our findings to human AML, a survey of Trib2 mRNA expression in human AMI patient samples identified elevated Trib2 expression in a subset of samples. Together, our data identify Trib2 as an oncogene in the pathogenesis of AML that functions by inactivating C/EBPa. The goals of this proposal are to determine the mechanism by which Trib2 induces C/EBPa degradation, determine the mechanism by which Trib2 induces AML, to identify the Trib2-expressing hematopoietic progenitors that initiate AML, and to identify genes that cooperate with Trib2 in the pathogenesis of AML. These studies should not only lead to a better understanding of the pathogenesis of AML, but should have direct translational utility as they will identify new targets for diagnosing and treating AML. Experiments described in this project will greatly benefit from extensive interactions with the other Project Leaders and their projects and will also make extensive use of the scientific cores.