REGULATION OF TUMOR NECROSIS FACTOR-MEDIATED AND FAS-MEDIATED APOPTOTIC CELL-DEATH BY A NOVEL CDNA, TR2(L)

A novel cDNA, TR2(L), isolated from murine NIH 3T3 fibroblasts, was fo und to modulate tumor necrosis factor (TNF)-mediated apoptosis in muri ne L929 fibrosarcoma cells. The full-length cDNA (853 bp) encodes a pr edicted coding region of 56 amino acids (6.3 kD), with 53.6% identity to the C-terminus of rat transcriptional activator FE65. When expresse d 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 t agging this protein with a 6xHis fragment to the N-terminus (designate d 6xH-TR2(L)). L929 cells which stably expressed 6xH-TR2(L) acquired a significantly enhanced TNF apoptotic response and increased genomic D NA fragmentation compared to control cells. Enhanced cell death also o ccurred in these 6xH-TR2(L)-expressing cells under serum starvation co nditions. In contrast, the anti-Fas/ActD-mediated apoptosis was blocke d by the 6xH-TR2(L) protein. Functional role of TR2(L) protein in regu lation of cancer cell susceptibility to TNF- and Fas ligand-mediated a poptosis is suggested. (C) 1996 Academic Press, Inc.