E3 ubiquitin-protein ligase RNF139 (RNF139)

E3-ubiquitin ligase; acts as a negative regulator of the cell proliferation through mechanisms between G2/M arrest and cell death. Required for MHC class I ubiquitination in cells expressing the cytomegalovirus protein US2 before dislocation from the endoplasmic reticulum (ER).

Affects SREBP processing by hindering the SREBP/SCAP complex translocation from the ER to the Golgi, thereby reducing SREBF2 target gene expression. Required for INSIG1 ubiquitination.