Involved in spindle disassembly; degradation of ubiquitinated proteins and protein export from the endoplasmic reticulum to the cytoplasm. Acts as a chaperone that collects ubiquitinated substrates. Has a role in the endoplasmic reticulum- associated degradation (ERAD) pathway. Required for the proteasome-dependent processing/activation of MGA2 and SPT23 transcription factors leading to the subsequent expression of OLE1. Has an additional role in the turnover of OLE1 where it targets ubiquitinated OLE1 and other proteins to the ERAD (PubMed:11733065; PubMed:11740563; PubMed:11813000; PubMed:11847109; PubMed:21070972; PubMed:21148305). Component of the ribosome quality control complex (RQC); a ribosome-associated complex that mediates ubiquitination and extraction of incompletely synthesized nascent chains for proteasomal degradation. CDC48 may provide the mechanical force that dislodges the polyubiquitinated nascent peptides from the exit channel (PubMed:23178123; PubMed:24261871). {ECO:0000269|PubMed:11733065; ECO:0000269|PubMed:11740563; ECO:0000269|PubMed:11813000; ECO:0000269|PubMed:11847109; ECO:0000269|PubMed:21070972; ECO:0000269|PubMed:21148305; ECO:0000269|PubMed:23178123; ECO:0000269|PubMed:24261871}.