title: Cdc48/p97 mediates UV-dependent turnover of RNA Pol II.
abstract: Cdc48/p97 is an essential ATPase whose role in targeting substrates to the ubiquitin-proteasome system (UPS) remains unclear. Existing models posit that Cdc48 acts upstream of UPS receptors. To address this hypothesis, we examined the association of ubiquitin (Ub) conjugates with 26S proteasomes. Unexpectedly, proteasomes isolated from cdc48 mutants contain high levels of Ub conjugates, and mass spectrometry identified numerous nonproteasomal proteins, including Rpb1, the largest subunit of RNA Pol II. UV-induced turnover of Rpb1 depends upon Cdc48-Ufd1-Npl4, Ubx4, and the uncharacterized adaptor Ubx5. Ubiquitinated Rpb1, proteasomes, and Cdc48 accumulate on chromatin in UV-treated wild-type cells, and the former two accumulate to higher levels in mutant cells, suggesting that degradation of Rpb1 is facilitated by Cdc48 at sites of stalled transcription. These data reveal an intimate coupling of function between proteasomes and Cdc48 that we suggest is necessary to sustain processive degradation of unstable subunits of some macromolecular protein complexes.
authors.affiliation: California Institute of Technology, Pasadena, CA 91125, USA. verma@caltech.edu
authors.forename: Rati
authors.initials: R
authors.lastname: Verma
authors.forename: Robert
authors.initials: R
authors.lastname: Oania
authors.forename: Ruihua
authors.initials: R
authors.lastname: Fang
authors.forename: Geoffrey T
authors.initials: GT
authors.lastname: Smith
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Deshaies
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D044842:Cullin Proteins / Q000378:metabolism / Q000502:physiology; D017353:Gene Deletion; D047908:Intracellular Signaling Peptides and Proteins; D008957:Models, Genetic; D016296:Mutagenesis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism / Q000502:physiology; D058767:Protein Unfolding; D012319:RNA Polymerase II / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination; D014466:Ultraviolet Rays; D000074405:Valosin Containing Protein
chemical_list: C480739:CUL3 protein, S cerevisiae; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; D047908:Intracellular Signaling Peptides and Proteins; D029701:Saccharomyces cerevisiae Proteins; C542871:UBX4 protein, S cerevisiae; C555925:UBX5 protein, S cerevisiae; D025801:Ubiquitin; D012319:RNA Polymerase II; C511736:RPB1 protein, S cerevisiae; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000251:Adenosine Triphosphatases; C000614177:CDC48 protein, S cerevisiae; D000074405:Valosin Containing Protein