FLASH is a protein recently shown to interact with the death effector domai
n of caspase-8 and is likely to be a component of the death-inducing signal
ing complex in receptor-mediated apoptosis, Here we show that antisense oli
gonucleotide-induced inhibition of FLASH expression abolished TNF-ru-induce
d activation of NF-KB in HEK293 cells, as determined by luciferase reporter
gene expression driven by a NF-KB responsive promoter. Conversely, overexp
ression of FLASH dose-dependently activated NF-KB, an effect suppressed by
dominant negative mutants of TRAF2, NIK, and IKK alpha, and partially by th
ose of TRAF5 and TRAF6, TRAF2 was co-immunoprecipitated with FLASH from the
cell extracts of HEK293 cells or HeLa cells stably expressing exogenous FL
ASH (HeLa/HA-FLASH), Furthermore, serial deletion mapping demonstrated that
a domain spanning the residues 856-1191 of FLASH activated NF-KB as effici
ently as the full-length and could directly bind to TRAF2 in vitro and in t
he transfected cells. Taken together, these results suggest that FLASH coor
dinates downstream NF-KB activity via a TRAF2-dependent pathway in the TNF-
alpha signaling.