Has an E3 ubiquitin ligase activity (PubMed:14578165, PubMed:16816390). Ubiquitinates DTNBP1 (dysbindin) and promotes its degradation (By similarity). May ubiquitinate BBS2 (By similarity). Ubiquitinates PIAS4/PIASY and promotes its degradation in keratinocytes treated with UVB and TNF-alpha (PubMed:14578165, PubMed:16816390)Also acts as a regulator of autophagy by mediating formation of unanchored 'Lys-63'-linked polyubiquitin chains that activate ULK1: interaction with AMBRA1 is required for ULK1 activation (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. It self-associates (By similarity). Interacts with DTNBP1 (By similarity). Interacts with PIAS4/PIASY upon treatment with UVB and TNF-alpha (PubMed:16816390). Interacts with AMBRA1; promoting activation of ULK1 through unanchored 'Lys-63'-linked polyubiquitin chains (By similarity). Localized in cytoplasmic bodies, often located around the nucleus. Ubiquitous. High expression in brain. By interferon alpha/UVB treatment. Ubiquitinated. Belongs to the TRIM/RBCC family.