E3 ubiquitin-protein ligase that regulates activation of NF- kappa-B and JNK and plays a central role in the regulation of cell survival and apoptosis (PubMed:10346818, PubMed:11784851, PubMed:12917689, PubMed:15383523, PubMed:18981220, PubMed:19150425, PubMed:19810754, PubMed:19918265, PubMed:19937093, PubMed:20047764, PubMed:20064526, PubMed:20385093, PubMed:20577214, PubMed:22212761). Catalyzes 'Lys-63'-linked ubiquitination of target proteins, such as BIRC3, IKBKE, MLST8, RIPK1 and TICAM1 (PubMed:23453969, PubMed:28489822). Is an essential constituent of several E3 ubiquitin- protein ligase complexes, where it promotes the ubiquitination of target proteins by bringing them into contact with other E3 ubiquitin ligases (PubMed:15383523, PubMed:18981220). Regulates BIRC2 and BIRC3 protein levels by inhibiting their autoubiquitination and subsequent degradation; this does not depend on the TRAF2 RING-type zinc finger domain (PubMed:11907583, PubMed:19506082). Plays a role in mediating activation of NF-kappa-B by EIF2AK2/PKR (PubMed:15121867). In complex with BIRC2 or BIRC3, promotes ubiquitination of IKBKE (PubMed:23453969). Acts as a regulator of mTORC1 and mTORC2 assembly by mediating 'Lys-63'-linked ubiquitination of MLST8, thereby inhibiting formation of the mTORC2 complex, while facilitating assembly of the mTORC1 complex (PubMed:28489822). Required for normal antibody isotype switching from IgM to IgG (By similarity). {ECO:0000250|UniProtKB:P39429, ECO:0000269|PubMed:10346818, ECO:0000269|PubMed:11784851, ECO:0000269|PubMed:11907583, ECO:0000269|PubMed:12917689, ECO:0000269|PubMed:15121867, ECO:0000269|PubMed:15383523, ECO:0000269|PubMed:18981220, ECO:0000269|PubMed:19150425, ECO:0000269|PubMed:19506082, ECO:0000269|PubMed:19810754, ECO:0000269|PubMed:19918265, ECO:0000269|PubMed:19937093, ECO:0000269|PubMed:20047764, ECO:0000269|PubMed:20064526, ECO:0000269|PubMed:20385093, ECO:0000269|PubMed:20577214, ECO:0000269|PubMed:22212761, ECO:0000269|PubMed:23453969, ECO:0000269|PubMed:28489822}. This is the function of TRAF2 (TNF receptor associated factor 2, ENSG00000127191).