Endoplasmic reticulum (ER) membrane anchored E3 ligase involved in the retrotranslocation and turnover of membrane and secretory proteins from the ER through a set of processes named ER-associated degradation (ERAD). This process acts on misfolded proteins as well as in the regulated degradation of correctly folded proteins. Enhances ionizing radiation-induced p53/TP53 stability and apoptosis via ubiquitinating MDM2 and AKT1 and decreasing AKT1 kinase activity through MDM2 and AKT1 proteasomal degradation. Regulates ER stress-induced autophagy, and may act as a tumor suppressor. Also plays a role in innate immune response by stimulating NF-kappa-B activity in the TLR2 signaling pathway. Ubiquitinates TRAF6 via the 'Lys-29'-linked polyubiquitination chain resulting in NF-kappa-B activation. Participates as well in T-cell receptor-mediated NF-kappa-B activation. In the presence of TNF, modulates the IKK complex by regulating IKBKG/NEMO ubiquitination leading to the repression of NF-kappa-B.