bri3 was identified to be a novel gene up-regulated in TNF-treated cells with suppressed subtractive hybridization (SSH) in our laboratory. Previous studies showed that overexpression of BR13 induced apoptosis in L929 cells. To further study the function of bri3, we disrupted its expression by expressing bri3 antisense RNA. The antisense RNA promoted resistance to TNF-induced cell death by more than 1000-fold in L929 cells, suggesting the involvement of BR13 in TNF-induced cell death in this cell line. Analysis of cell death caused by other apoptotic inducers showed that the effect of BR13 antisense RNA is highly specific to TNF-induced cell death. Taken together, bri3 appears to play an important role in TNF-induced cell death. Finally, we reported here that BR13 may be localized to lysosome and function through lysosome. (C) 2003 Published by Elsevier Inc.