NEDD8 links cullin-RING ubiquitin ligase function to the p97 pathway

Area of Science:

• Molecular Biology
• Protein Degradation Pathways
• Ubiquitin Signaling

Background:

• AAA+ ATPase p97 and its cofactors are implicated in protein degradation.
• The precise targets and functions of many p97 cofactors remain unclear.
• The p97 pathway has been previously linked to cullin-RING ubiquitin ligases (CRLs).

Purpose of the Study:

• To elucidate the function of the p97 cofactor UBXD7.
• To investigate the mechanism linking the p97 pathway to CRLs.
• To identify the role of UBXD7 in mediating interactions between p97 and CRLs.

Main Methods:

• Investigated the interaction between human UBXD7 and the p97-CRL complex.
• Utilized yeast ortholog Ubx5 to study cofactor function.
• Disrupted the ubiquitin-interacting motif (UIM) of Ubx5 to assess CRL binding and substrate degradation.

Main Results:

• UBXD7 mediates the p97-CRL interaction through its UIM.
• UBXD7 and Ubx5 bind to the active, NEDD8- or Rub1-modified form of cullins.
• Disruption of the Ubx5 UIM impairs CRL binding and Cul3 substrate degradation.

Conclusions:

• UBXD7 is a conserved p97 cofactor that links the p97 pathway to CRLs.
• The UIM of UBXD7 is crucial for CRL interaction and subsequent substrate degradation.
• NEDD8 modification of cullins plays a conserved role in connecting CRLs to the p97 degradation machinery.