Has E3 ubiquitin-protein ligase activity. Acts as an anti-apoptotic regulator of the JNK pathway by ubiquitinating and promoting the degradation of SH3RF1, a scaffold protein that is required for pro-apoptotic JNK activation (PubMed:22128169). Facilitates TNF-alpha-mediated recruitment of adapter proteins TRADD and RIPK1 to TNFRSF1A and regulates PAK4 protein stability via inhibition of its ubiquitin-mediated proteasomal degradation. Inhibits PPP1CA phosphatase activity (By similarity). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Interacts with FASLG and PPP1CA. Interacts with PAK4 and TNFRSF1A (By similarity). Interacts with DLK1, MAP3K10, MAPK8IP1/JIP1, MAPK8IP2/JIP2 and MAPK8IP3/JIP3. Interacts with RAC1 (both active GTP- or inactive GDP-bound forms) (PubMed:22128169). The RING finger domain is required for ubiquitin ligase activity and autoubiquitination. Autoubiquitinated. Belongs to the SH3RF family.