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The 19 S proteasomal subunit POH1 contributes to the regulation of c-Jun ubiquitination, stability, and subcellular localization.

The AP1 (activator protein 1) transcription factor, c-Jun, is an important regulator of cell proliferation, differentiation, survival, and death. Its activity is regulated both at the level of transcription and post-translationally through phosphorylation, sumoylation, and targeted degradation. The degradation of c-Jun by the ubiquitin proteasome pathway has been well established. Here, we report that POH1, a subunit of the 19 S proteasome lid with a recently described deubiquitinase activity, is a regulator of c-Jun. Ectopic expression of POH1 in HEK293 cells decreased the level of c-Jun ubiquitination, leading to significant accumulation of the protein and a corresponding increase in AP1-mediated gene expression. The stabilization also correlated with a redistribution of c-Jun in the nucleus. These effects were reduced by mutation of a cysteine residue in the Mpr1 pad1 N-terminal plus motif of POH1 (Cys-120) and appeared to be selective for c-Jun, because POH1 had no effect on other proteasomal substrates. Our results identify a novel mechanism of c-Jun regulation in mammalian cells.

Pubmed ID: 16569633


  • Nabhan JF
  • Ribeiro P


The Journal of biological chemistry

Publication Data

June 9, 2006

Associated Grants


Mesh Terms

  • Base Sequence
  • Cell Line
  • DNA Primers
  • Genes, Reporter
  • Humans
  • Immunoprecipitation
  • Proteasome Endopeptidase Complex
  • Proto-Oncogene Proteins c-jun
  • Reverse Transcriptase Polymerase Chain Reaction
  • Subcellular Fractions
  • Trans-Activators
  • Ubiquitin