Disruption of the arf transcriptional activator dmp1 facilitates cell immortalization, ras transformation, and tumorigenesis

Academic Article
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publication date

  • July 2000

abstract

  • The DMP1 transcription factor induces the ARF tumor suppressor gene in mouse fibroblasts, leading to cell cycle arrest in a p53-dependent manner. We disrupted sequences encoding the DNA-binding domain of DMP1 in mouse embryonic stem cells and derived animals lacking the functional protein. DMP1-null animals are small at birth, and males develop more slowly than their wild-type littermates. Some adult animals exhibit seizures and/or obstuctive uropathy, each of unknown cause. The growth of explanted DMP1-null mouse embryo fibroblasts (MEFs) is progressively retarded as cells are passaged in culture on defined transfer protocols; but, unlike the behavior of normal cells, p19(ARF), Mdm2, and p53 levels remain relatively low and DMP1-null MEFs do not senesce. Whereas the establishment of cell lines from MEFs is usually always accompanied by either p53 or ARF loss of function, continuously passaged DMP1-null cells readily give rise to established 3T3 and 3T9 cell lines that retain wild-type ARF and functional p53 genes. Early-passage DMP1-null cells, like MEFs from either ARF-null or p53-null mice, can be morphologically transformed by oncogenic Ha-Ras (Val-12) alone. Splenic lymphocytes harvested from both DMP1-null and ARF-null mice exhibit enhanced proliferative responses in long-term cultures when stimulated to divide with antibody to CD3 and interleukin-2. Although only 1 of 40 DMP1-null animals spontaneously developed a tumor in the first year of life, neonatal treatment with dimethylbenzanthracene or ionizing radiation induced tumors of various histologic types that were not observed in similarly treated DMP1(+/+) animals. Karyotypic analyses of MEFs and lymphomas from DMP1-null animals revealed pseudodiploid chromosome numbers, consistent with the retention of wild-type p53. Together, these data suggest that ARF function is compromised, but not eliminated, in animals lacking functional DMP1.