The role of Ndy1 in epigenetic gene silencing and stem cell biology

对MoMuLV诱导的大鼠T细胞淋巴瘤中常见整合位点的全基因组筛选导致了一个新的癌基因Ndy1(尚未死亡-1)的鉴定，也被称为Fbxl10、JHDM1B或Kdm2b，它是本提案的主题。NDY1编码1336个氨基酸的染色质相关组蛋白H3去甲基酶，含有N-termal JmjC结构域、CXXC锌指结构域、PHD2锌指、F-box和富含亮氨酸的重复序列(LRR)，在胚胎干细胞(ES细胞)和造血干细胞(HSCs)等干细胞中表达最高。Ndy1的去甲基酶活性是组蛋白H3K36(Me2)和H3K4(Me3)所特有的，它是JmjC结构域依赖的。我们的研究已经将Ndy1与逆转录病毒诱导的啮齿动物造血肿瘤的诱导联系起来。此外，对其在现有数据库中的表达的研究表明，Ndy1在各种人类肿瘤中过表达，主要是白血病(AML和B细胞和T细胞白血病)、精原细胞瘤，以及较小程度的乳腺癌。该实验室的研究还表明，Ndy1的过表达通过JmjC结构域依赖的过程抑制复制和癌基因诱导的衰老，并且它的敲除促进衰老。最后，它的过度表达促进了全基因组的表观遗传学变化，并改变了与细胞增殖和生存有关的基因的表达。这些数据结合在一起，表明Ndy1是一个有助于人类癌症发展的癌基因。该实验室的其他研究表明，在ES干细胞中，Ndy1的表达随着分化的进行而急剧下降，并且这些ES细胞中外源Ndy1的表达干扰了分化，但并不完全阻止分化。这些发现表明Ndy1在干细胞的周期中起着重要作用。与这些数据一致的是，过度表达Ndy1的细胞对氧化应激和缺氧具有抵抗力，这是干细胞的特征。拟议的实验将使用分子生物学和细胞培养技术，以及生物信息学和动物模型，以解决Ndy1在基因表达的表观遗传调控和干细胞生物学中的作用。

A genome wide screen for loci of common integration in MoMuLV-induced rat T cell lymphomas, led to the identification of a novel oncogene, Ndy1 (Not dead yet-1), also known as FBXL10, JHDM1B, or KDM2B, which is the subject of this proposal. Ndy1 encodes a 1336 amino acid chromatin-associated histone H3 demethylase, which contains an N-termal JmjC domain, a CXXC zinc finger domain, a PHD2 zinc finger, an F-box, and a leucine-rich repeat (LRR) and is expressed most highly in stem cells, such as embryonal stem cells (ES cells) and hematopoietic stem cells (HSCs). The demethylase activity of Ndy1 is specific for histone H3K36 (me2) and H3K4(me3) and it is JmjC domain-dependent. Our studies have linked Ndy1 to the induction of retrovirus-induced rodent hematopoietic neoplasms. Moreover, examination of its expression in existing databases has shown that Ndy1 is overexpressed in a variety of human tumors, primarily leukemias (AML and B and T cell leukemias), seminomas, and to a lesser extent, breast cancer. Studies from this laboratory have also shown that overexpression of Ndy1 inhibits both replicative and oncogene-induced senescence via a JmjC domain-dependent process and that its knockdown promotes senescence. Finally, its overexpression promotes genome wide epigenetic changes and alters the expression of genes involved in cell proliferation and survival. These data combined, suggest that Ndy1 is an oncogene that contributes to the development of human cancer. Other studies from this laboratory have shown that the expression of Ndy1 in ES stem cells, declines precipitously with differentiation and that exogenous Ndy1 expression in these ES cells interferes with, but does not completely block differentiation. These findings suggest that Ndy1 plays an important role in the cycling of stem cells. In agreement with these data, cells overexpressing Ndy1 are resistant to oxidative stress and hypoxia, features characteristic of stem cells. The proposed experiments will employ molecular biology and cell culture technologies, as well as bioinformatics and animal models to address the role of Ndy1 in the epigenetic regulation of gene expression and in the biology of stem cells.