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

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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.