Mobilization of Processed, Membrane-Tethered SPT23 Transcription Factor by CDC48 super(UFD1/NPL4), a Ubiquitin-Selective Chaperone

The OLE pathway of yeast regulates the level of the ER-bound enzyme Delta 9-fatty acid desaturase OLE1, thereby controlling membrane fluidity. A central component of this regulon is the transcription factor SPT23, a homolog of mammalian NF- Kappa B. SPT23 is synthesized as an inactive, ER membrane-a...

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Bibliographic Details
Published in:Cell 2001-11, Vol.107 (5), p.667-677
Main Authors: Rape, M, Hoppe, T, Gorr, I, Kalocay, M, Richly, H, Jentsch, S
Format: Article
Language:English
Subjects:
Cdc48 protein
OLE1 gene
Saccharomyces cerevisiae
Spt23 protein
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Summary:The OLE pathway of yeast regulates the level of the ER-bound enzyme Delta 9-fatty acid desaturase OLE1, thereby controlling membrane fluidity. A central component of this regulon is the transcription factor SPT23, a homolog of mammalian NF- Kappa B. 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 super(UFD1/NPL4) complex. Remarkably, this enzyme binds preferentially ubiquitinated substrates, suggesting that CDC48 super(UFD1/NPL4) is qualified to selectively remove ubiquitin conjugates from protein complexes.
ISSN:0092-8674