E3 ubiquitin-protein ligase that mediates ubiquitination of TFRC, CD86, FAS and MHC class II proteins, such as HLA-DR alpha and beta, and promotes their subsequent endocytosis and sorting to lysosomes via multivesicular bodies (PubMed:18389477, PubMed:18305173, PubMed:21220452, PubMed:35045264). By constitutively ubiquitinating MHC class II proteins in immature dendritic cells, down-regulates their cell surface localization thus sequestering them in the intracellular endosomal system. Also regulates insulin sensitivity by controlling surface expression of the insulin receptor subunit beta/INSR by direct ubiquitination and degradation (PubMed:27577745). {ECO:0000269|PubMed:14722266, ECO:0000269|PubMed:18305173, ECO:0000269|PubMed:18389477, ECO:0000269|PubMed:19117940, ECO:0000269|PubMed:21220452, ECO:0000269|PubMed:27577745, ECO:0000269|PubMed:35045264}. (Microbial infection) Plays a role in iron metabolism by regulating the levels of the transferrin receptor TFRC during human cytomegalovirus infection, subsequently contributing to a proviral effect. . This is the function of MARCHF1 (membrane associated ring-CH-type finger 1, ENSG00000145416).