E3 ubiquitin-protein ligase which promotes K48-linked polyubiquitination of protein methyltransferase PRMT1, leading to PRMT1 degradation (PubMed:29186683). This suppresses methylation of the PRMT1 substrate MAP3K5/ASK1, promoting its activation and increasing MAP3K5-dependent cell death induced by oxidative stress (PubMed:29186683). TRIM48-mediated ubiquitination of PRMT1 also suppresses methylation of FOXO1 by PRMT1, leading to inhibition of FOXO1 transcriptional activity (PubMed:29186683). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Interacts with PRMT1; the interaction leads to ubiquitination of PRMT1 by TRIM48 (PubMed:29186683). Interacts with MAP3K5 (PubMed:29186683). Interacts with STRAP (PubMed:29186683). Belongs to the TRIM/RBCC family. Truncated N-terminus. Truncated N-terminus. Extended C-terminus.