May play a role in the ER-associated protein degradation pathway (ERAD) possibly via its interaction with ER-localized proteins ubxn-4 and cdc-48.1 and/or cdc48.2, providing a link between the polyubiquitinated ERAD substrates and the proteasome (PubMed:19822669). Also plays an important role in the regulation of other protein degradation mechanisms and pathways including ubiquitin-proteasome system (UPS) and autophagy (By similarity). Mediates the proteasomal targeting of misfolded or accumulated proteins for degradation by binding (via UBA domain) to their polyubiquitin chains and by interacting (via ubiquitin-like domain) with the subunits of the proteasome (By similarity). Collaborates with POST (F36D4.5) in the export of ubiquitinated proteins from the nucleus to the cytoplasm (PubMed:29666234). Also acts as a regulator of DNA repair by inhibiting homologous recombination repair, thereby redirecting double-strand break repair toward non-homologous end joining (NHEJ) (PubMed:30612738). Expressed in the pharynx, hypodermis, intestine and head neurons (PubMed:29666234). Upon ER stress, expressed predominantly in pharyngeal muscle, hypodermis and intestine (PubMed:19822669). Induced upon ER stress. RNAi-mediated knockdown causes a reduction in lifespan (PubMed:19822669). Induces ER stress characterized by the expression of hsp-4, the accumulation of ubiquitinated proteins and an increase in ubxn-4 expression (PubMed:19822669). Mutants display increased homologous recombination repair in response to DNA damage compared to wild-type worms (PubMed:30612738). Worms lacking both POST (F36D4.5) and ubql-1 have a shorter lifespan and display an accumulation of ubiquitinated proteins in the nucleus (PubMed:29666234).