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Free keywords:
CDC48; chaperone; OLE pathway; segregase; ubiquitin
Abstract:
The OLE pathway of yeast regulates the abundance of the ER- bound enzyme Delta-9 fatty acid desaturase OLE1, thereby controlling unsaturated fatty acid pools and membrane fluidity. Previously, we showed that this pathway is exquisitely regulated by the ubiquitin/proteasome system. Activation of the pathway involves proteasomal processing of a membrane-bound transcription factor and the subsequent mobilization of the cleaved, ubiquitylated transcription factor from its partner molecule by CDC48(UFD1/NPL4), a ubiquitin-selective chaperone- like enzyme. Here we report that the OLE1 protein itself is naturally short-lived and is degraded by ubiquitin/proteasome- dependent ER-associated degradation (ERAD). We found that CDC48(UFD1/NPL4) plays a second role in the OLE pathway by mediating ERAD of OLE1 Intriguingly, other ERAD substrates also require CDC48UFD1/NPL4 for degradation, indicating that this enzyme is a novel, constitutive component of the ERAD machinery. We propose that CDC48(UFD1/NPL4) functions as a segregase that liberates ubiquitylated proteins from non- modified partners.
