TRAF1 is a TNF inducible regulator of NF‐κB activation

Abstract
Tumor necrosis factor receptor (TNFR)‐associated factor TRAF1 was first identified as a component of the TNFR2 signalling complex. Unlike the other members of the TRAF family, TRAF1 lacks the N‐terminal ring finger motif and has a tissue specific expression. Here we demonstrate that expression of TRAF1 is induced by TNF and the protein kinase C (PKC) activator PMA, but not by interleukin‐1 (IL‐1). TNF‐induced upregulation of TRAF1 could be prevented by pretreatment of the cells with the proteasome inhibitor MG‐132, whereas the PKC inhibitor Ro31‐8220 was without effect. Interestingly, overexpression of TRAF1 in HEK293T completely prevented NF‐κB activation induced by TNF, IL‐1, or overexpression of TRAF2 or TRAF6. These data suggest that inducible expression of TRAF1 may serve a negative regulatory function in NF‐κB signalling pathways.