Analysis of chaperone-assisted ubiquitylation

Abstract

Molecular chaperones are traditionally viewed as cellular protein folding and assembly factors. However, in recent years it became more and more evident that certain chaperones, i.e., members of the 70-kDa heat shock protein family (Hsp70s), participate very actively in protein degradation and in this way significantly contribute to protein homeostasis. Degradation is often initiated through a close cooperation of Hsp70s with chaperone-associated ubiquitin ligases. This results in the ubiquitylation of chaperone-bound client proteins and triggers client sorting toward the proteasome or the autophagosome-lysosome system. Here, we describe the in vitro reconstitution of chaperone-assisted ubiquitylation, which allows analyzing molecular details of this important proteostasis mechanism.