Has E3 ubiquitin-protein ligase activity (PubMed:24130170). 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 (PubMed:24130170). Inhibits PPP1CA phosphatase activity (PubMed:19945436, PubMed:19389623). 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 (PubMed:19389623, PubMed:19807924, PubMed:19945436). Interacts with PAK4 and TNFRSF1A (PubMed:24130170). Interacts with DLK1, MAP3K10/MLK2, MAPK8IP1/JIP1, MAPK8IP2/JIP2 and MAPK8IP3/JIP3. Interacts with RAC1 (both active GTP- or inactive GDP-bound forms) (By similarity). Heart (at protein level). Up-regulated in colon cancer tissues as compared to normal colon tissues (at protein level). Testis. In the heart, present in the apex, left atrium, right atrium, left ventricle and right ventricle, but not in the aorta. The RING finger domain is required for ubiquitin ligase activity and autoubiquitination. Autoubiquitinated. Belongs to the SH3RF family. Extended N-terminus. Truncated C-terminus.