Component of the DSC E3 ubiquitin ligase complex which is required for the sre1 transcriptional activator proteolytic cleavage to release the soluble transcription factor from the membrane in low oxygen or sterol conditions. The complex also plays an important role in the multivesicular body (MVB) pathway and functions in a post-endoplasmic reticulum pathway for protein degradation. Protein modification; protein ubiquitination. Component of the DSC E3 ubiquitin ligase complex composed of dsc1, dsc2, dsc3 and dsc4.