Mobilization of processed, membrane-tethered SPT23 transcription factor by CDC48(UFD1/NPL4), a ubiquitin-selective chaperone.

The OLE pathway of yeast regulates the level of the ER-bound enzyme Delta9-fatty acid desaturase OLE1, thereby controlling membrane fluidity. A central component of this regulon is the transcription factor SPT23, a homolog of mammalian NF-kappaB. SPT23 is synthesized as an inactive, ER membrane-anchored precursor that is activated by regulated ...
ubiquitin/proteasome-dependent processing (RUP). We now show that SPT23 dimerizes prior to processing and that the processed molecule, p90, retains its ubiquitin modification and initially remains tethered to its unprocessed, membrane-bound SPT23 partner. Subsequently, p90 is liberated from its partner for nuclear targeting by the activity of the chaperone-like CDC48(UFD1/NPL4) complex. Remarkably, this enzyme binds preferentially ubiquitinated substrates, suggesting that CDC48(UFD1/NPL4) is qualified to selectively remove ubiquitin conjugates from protein complexes.
Mesh Terms:
Active Transport, Cell Nucleus, Adenosine Triphosphatases, Cell Cycle Proteins, Cell Membrane, Dimerization, Fatty Acid Desaturases, Fungal Proteins, Genes, Reporter, Macromolecular Substances, Membrane Proteins, Models, Biological, Molecular Chaperones, Nuclear Pore Complex Proteins, Nuclear Proteins, Nucleocytoplasmic Transport Proteins, Protein Binding, Protein Precursors, Protein Processing, Post-Translational, Protein Structure, Tertiary, Proteins, Saccharomyces cerevisiae Proteins, Trans-Activators, Transcription Factors, Two-Hybrid System Techniques, Ubiquitin, Yeasts
Cell
Date: Nov. 30, 2001
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