Regulation of tumor necrosis factor- and fas-mediated apoptotic cell death by a novel cDNA, TR2(L)

A novel cDNA, TR2(L), isolated from murine NIH 3T3 fibroblasts, was found to modulate tumor necrosis factor (TNF)-mediated apoptosis in murine L929 fibrosarcoma cells. The full-length cDNA (853 bp) encodes a predicted coding region of 56 amino acids (6.3 kD), with 53.6% identity to the C-terminus of rat transcriptional activator FE65. When expressed stably in L929 cells, TR?L protein inhibited TNF cytotoxic response. In contrast, TR2(L) enhanced anti-Fas antibodies/ actinomycin D (ActD)-mediated L929 apoptosis. Alteration of TR2(L) function occurred by tagging this protein with a 6xHis fragment to the N-terminus (designated 6xH-TR2(L)). L929 cells which stably expressed 6xH-TR2(L) acquired a significantly enhanced TNF apoptotic response and increased genomic DNA fragmentation compared to control cells. Enhanced cell death also occurred in these 6xH-TR2(L)-expressing cells under serum starvation conditions. In contrast, the anti-Fas/ActD-mediated apoptosis was blocked by the 6xH-TR2(L) protein. Functional role of TR2(L) protein in regulation of cancer cell susceptibility to TNF- and Fas ligand-mediated apoptosis is suggested. (C) 1996 Academic Press, Inc.