TNF receptor-associated factor 1 is a positive regulator of the NF-kappaB alternative pathway

Tumor necrosis factor receptor-associated factor 1 (TRAF1) is unique among the members of the TRAF family, as it lacks the N-terminal RING/zinc-finger domain. Also the function of TRAF1 is not clearly established, with many papers reporting contradictory results. Here we show that TRAF1 interacts with BAFF receptor, a member of the TNF receptor family, and positively regulates activation of the alternative NF-kappaB pathway. Ectopic expression of TRAF1 causes degradation of TRAF3, stabilization of NIK, and processing of p100 to produce the mature form p52. In addition, we show that knocking-down expression of TRAF1 in the Hodgkin's disease derived cell line L1236, interfere with p100 processing and with p52 mediate gene transcription. Collectively these results support a role for TRAF1 as a positive regulator of the NF-kappaB alternative pathway.