E3 ubiquitin-protein ligase which transfers ubiquitin to substrates promoting their degradation. Part of the nuclear inner membrane (INM)-specific branch of the ER-associated degradation (ERAD) pathway, required for the elimination of misfolded proteins in the INM, a specialized ER subdomain. Required for ERG11 degradation (PubMed:25236469). Negative regulator of SPS-sensor signaling. Together with ASI2 and ASI3, prevents the unprocessed precursor forms of STP1 and STP2 that escape cytoplasmic anchoring from inducing SPS-sensor-regulated genes in the absence of inducing signals (PubMed:16735580, PubMed:17085444). Controls amino acid permease (AAP) gene expression in response to amino acid availability, a process mediated by the transcription factors STP1 and STP1 (PubMed:11454748). 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. Component of the Asi complex, which contains ASI1, ASI2 and ASI3 (PubMed:25236469). Interacts directly with ASI3 (PubMed:17085444). Glycosylation is not required for ASI1 function.