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

通过对momulv诱导的大鼠T细胞淋巴瘤中共同整合位点的全基因组筛选，发现了一种新的致癌基因Ndy1（未死亡-1），也称为FBXL10、JHDM1B或KDM2B，这是本提案的主题。Ndy1编码一个1336个氨基酸的染色质相关组蛋白H3去甲基化酶，包含一个n端JmjC结构域、一个CXXC锌指结构域、一个PHD2锌指结构域、一个F-box和一个富含亮氨酸的重复序列（LRR），在干细胞中表达最多，如胚胎干细胞（ES细胞）和造血干细胞（hsc）。Ndy1的去甲基酶活性对组蛋白H3K36 （me2）和H3K4（me3）具有特异性，并且依赖于JmjC结构域。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，对现有数据库中Ndy1表达的研究表明，Ndy1在多种人类肿瘤中过表达，主要是白血病（AML、B细胞和T细胞白血病）、精原细胞瘤，以及在较小程度上乳腺癌。该实验室的研究还表明，Ndy1的过表达通过JmjC结构域依赖过程抑制复制性和癌基因诱导的衰老，其敲低促进衰老。最后，它的过表达促进全基因组的表观遗传变化，改变参与细胞增殖和存活的基因的表达。这些数据综合起来表明，Ndy1是一种致癌基因，有助于人类癌症的发展。本实验室的其他研究表明，Ndy1在胚胎干细胞中的表达随着分化而急剧下降，外源Ndy1在这些胚胎干细胞中的表达会干扰分化，但不会完全阻断分化。这些发现表明Ndy1在干细胞的循环中起着重要作用。与这些数据一致的是，过表达Ndy1的细胞能够抵抗氧化应激和缺氧，这是干细胞的特征。拟议的实验将采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来解决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.