E3 ubiquitin ligase that plays a role in several processes including innate antiviral immnity, cell migration and chemotaxis (PubMed:23077300, PubMed:34142270). Acts as a 'Lys-63'-specific ubiquitin ligase for MAPK1/ERK2 and MAPK3/ERK1, promoting their activation by facilitating their interaction with MAP2K1 and MAP2K2 (PubMed:34497368). Also plays a role in cell migration and chemotaxis by acting as a stable focal adhesion component upon recruitment by multi-adapter protein paxillin/PXN (PubMed:25015296). Functions in the RIGI-mediated interferon induction pathway upstream or at the level of MAVS (PubMed:23077300). Inhibits NF-kappa-B activation by turnover of 'Lys-63'-linked ubiquitination of MAP3K7/TAK1. Mechanistically, prevents TRIM8 cytoplasmic translocation and thus inhibits TRIM8- mediated 'Lys-63'-linked polyubiquitination of MAP3K7/TAK1 in the cytoplasm (PubMed:34871740). Also plays an important regulatory effect on the activation of hepatic stellate cells (HSCs). {ECO:0000269|PubMed:23077300, ECO:0000269|PubMed:25015296, ECO:0000269|PubMed:34142270, ECO:0000269|PubMed:34497368, ECO:0000269|PubMed:34871740}. This is the function of TRIM15 (tripartite motif containing 15, ENSG00000204610).