Tumor suppressor gene identification using retroviral insertional mutagenesis in Blm-deficient mice

Abstract

Retroviral insertional mutagenesis preferentially identifies oncogenes rather than tumor suppressor (TS) genes, presumably because a single retroviral-induced mutation is sufficient to activate an oncogene and initiate a tumor, whereas two mutations are needed to inactivate a TS gene. Here we show that TS genes can be identified by insertional mutagenesis when the screens are performed in Blm-deficient backgrounds. Blm-deficient mice, like Bloom syndrome patients, have increased frequencies of mitotic recombination owing to a mutation in the RecQ proteinlike-3 helicase gene. This increased mitotic recombination increases the likelihood that an insertional mutation in one allele of a TS gene will become homozygoused by nonsister chromatid exchange and the homozygosity of the insertion provides a marker for identifying the TS gene. We also show that known as well as novel TS genes can be identified by insertional mutagenesis in Blm-deficient mice and identify two JmjC family proteins that contribute to genome stability in species as evolutionarily diverse as mammals and Caenorhabditis elegans.

Members of a family of JmjC domain-containing oncoproteins immortalize embryonic fibroblasts via a JmjC domain-dependent process

“…A genome-wide screen of 44 MoMuLVinduced T cell lymphomas for novel targets of proviral DNA integration yielded clones of 149 independent provirus integrations. Six of these integrations, cloned from five independent tumors, had targeted a gene we named Ndy1, also known as FBXL10 or JHDM1B (9,10,16,17). Two of them were cloned from a single tumor, D0, suggesting that this tumor consists of at least two populations of cells, both of which carry an inte-grated provirus in this locus.…”

“…Ndy1 encodes a protein that contains a JmjC domain (9,10,16,17), a CXXC zinc finger, a PHD zinc finger, a proline-rich region (PRR), an F-box, and a leucine-rich repeat (LRR) (Fig. 1 A and ref.…”

“…Some JmjC domain-containing histone demethylases have been linked to cancer (14)(15)(16). However, the mechanisms of their oncogenic activities are not well understood.…”

Depletion of JMJD5 sensitizes tumor cells to microtubule-destabilizing agents by altering microtubule stability

“…JMJD5 was initially identified as a putative tumor suppressor that regulates genome integrity in Blm-deficient mice, 46 and JMJD5 overexpression inhibits cell growth and tumorigenicity in hepatocellular carcinoma cells. 32 However, in lung, colon and breast cancers, JMJD5 functions as a putative oncogene that promotes cancer cell proliferation, invasion and cellular metabolism.…”

Mutation of C/EBPα predisposes to the development of myeloid leukemia in a retroviral insertional mutagenesis screen

“…56 These functional observations and the fact that its relatives Chd2, Chd3, and Chd9 have been identified as CISs in MoMuLV-based RIM screens suggest that Chd4 is indeed a likely oncogene. 48,57 Rag2 encodes the recombination activating gene 2 (Rag2), which in concert with Rag1 is directly involved in V(D)J recombination in lymphoid cells. Rag2 expression is normally strictly confined to lymphoid cells, and it has been suggested that inappropriate induction of the Rag complex could induce genomic instability due to unauthorized recombination.…”