Has an E3 ubiquitin ligase activity (, ). Ubiquitinates DTNBP1 (dysbindin) and promotes its degradation . May ubiquitinate BBS2 . Ubiquitinates PIAS4/PIASY and promotes its degradation in keratinocytes treated with UVB and TNF-alpha (By similarity). 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 .
(Microbial infection) May play a significant role in mediating the biological activity of the HIV-1 Tat protein in vivo . Binds specifically to the activation domain of HIV-1 Tat and can also interact with the HIV-2 and EIAV Tat proteins in vivo .
Subcellular locations: Cytoplasm
Localized in cytoplasmic bodies, often located around the nucleus.
Spleen, thymus, prostate, testis, ovary, intestine, colon and skeletal muscle.