Bridging factor involved in ER-associated protein degradation (ERAD); bridges the cytosolic Cdc48p-Npl1p-Ufd1p ATPase complex and the membrane associated Ssm4p and Hrd1p ubiquitin ligase complexes; contains a UBX (ubiquitin regulatory X) domain and a ubiquitin-associated (UBA) domain; redistributes from the ER to lipid droplets during the diauxic shift and stationary phase; required for the maintenance of lipid homeostasis
Saccharomyces cerevisiae (S288c)


UBX domain-containing protein that interacts with Cdc48p; involved in degradation of polyubiquitinated proteins via the ERAD (ER-associated degradation) pathway; modulates the Cdc48p-Nplp-Ufd1p AAA ATPase complex during its role in delivery of misfolded proteins to the proteasome; protein abundance increases in response to DNA replication stress
GO Process (2)
GO Function (1)
GO Component (3)
Saccharomyces cerevisiae (S288c)

Synthetic Growth Defect

A genetic interaction is inferred when mutations in separate genes, each of which alone causes a minimal phenotype, result in a significant growth defect under a given condition when combined in the same cell.


Ubx4 modulates cdc48 activity and influences degradation of misfolded proteins of the endoplasmic reticulum.

Alberts SM, Sonntag C, Schaefer A, Wolf DH

Misfolded proteins of the secretory pathway are recognized in the endoplasmic reticulum (ER), retrotranslocated into the cytoplasm, and degraded by the ubiquitin-proteasome system. Right after retrotranslocation and polyubiquitination, they are extracted from the cytosolic side of the ER membrane through a complex consisting of the AAA ATPase Cdc48 (p97 in mammals), Ufd1, and Npl4. This complex delivers misfolded proteins to ... [more]

J. Biol. Chem. Jun. 12, 2009; 284(24);16082-9 [Pubmed: 19359248]


  • Low Throughput

Ontology Terms

  • phenotype: vegetative growth (APO:0000106)
  • phenotype: resistance to chemicals (APO:0000087)

Additional Notes

  • double mutants show an increase in sensitivity to DTT

Curated By

  • BioGRID