The ubiquitin-homology protein, DAP-1, associates with tumor necrosis factor receptor (p60) death domain and induces apoptosis

The tumor necrosis factor receptor, p60 (TNF-R1), transduces death signals via the association of its cytoplasmic domain with several intracellular pr oteins. By screening a mammalian cDNA library using the yeast two-hybrid cl oning technique, we isolated a ubiquitin-homology protein, DAP-1, which spe cifically interacts with the cytoplasmic death domain of TNF-R1. Sequence a nalysis reveals that DAP-1 shares striking sequence homology with the yeast SMT3 protein that is essential for the maintenance of chromosome integrity during mitosis (Meluh, P. B., and Koshland, D. (1995) Mel. Biol. Cell 6, 7 93-807). DAP-1 is nearly identical to PIC1, a protein that interacts with t he PML tumor suppressor implicated in acute promyelocytic leukemia (Boddy, M. N., Howe, K., Etkin, L. D., Solomon, E., and Freemont, P. S. (1996) Onco gene 13, 971-982), and the sentrin protein, which associates with the Fas d eath receptor (Okura, T., Gong, L., Kamitani, T., Wada, T., Okura, I., Wei, C. F., Chang, H. M., and Yeh, E. T. (1996) J. Immunol. 157, 4277-4281). Th e in vivo interaction between DAP-1 and TNF-R1 was further confirmed in mam malian cells. In transient transfection assays, overexpression of DAP-1 sup presses NF-kappa B/Rel activity in 293T cells, a human kidney embryonic car cinoma cell line. Overexpression of either DAP-1 or sentrin causes apoptosi s of TNF-sensitive L929 fibroblast cell line, as well as TNF-resistant oste osarcoma cell line, U20S. Furthermore, the dominant negative Fas-associated death domain protein (FADD) protein blocks the cell death induced by eithe r DAP-1 or FADD. Collectively, these observations highly suggest a role for DAP-1 in mediating TNF-induced cell death signaling pathways, presumably t hrough the recruitment of FADD death effector.