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Faf2/Ubx2 potentiates p97/Cdc48 segregase activity via functional priming and reinforcement of the UT3 domain in Ufd1

Ren, Y.; Zheng, Q.; Duan, Y.; Xu, Z.; Qu, Q.; Weng, Y.; Cui, S.; Yu, Y.; Pan, M.; Liu, L.

2026-02-27 biochemistry
10.64898/2026.02.26.708172 bioRxiv
Show abstract

The AAA+ segregase p97/Cdc48 extracts poly-ubiquitinated proteins from entrenched cellular environments to maintain proteostasis. However, its functional capacity is not uniform; extracting substrates from dense assemblies like stress granules or membrane necessitates a fully potentiated state. Here, using precisely synthesized ubiquitinated substrates, we show that the Faf2/Ubx2 cofactor hyperactivates p97/Cdc48, lowering its minimal ubiquitin chain requirement and broadening linkage specificity. Cryo-EM analysis of the activated complex demonstrates that Faf2/Ubx2 potentiates p97/Cdc48 segregase activity by structurally remodeling the substrate recognition module (K48-diUbProx) and priming its engagement with the AAA+ motor (p97/Cdc48-Npl4). These coordinated actions establish a pump-unit architecture that drives efficient substrate processing. Our findings illuminate a conserved mechanism that unlocks the maximal capacity of p97/Cdc48 and provide a blueprint for therapeutically targeting its hyper-activated state in disease.

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