Ubiquitin Proteasome System The ubiquitin proteasome system (UPS) consists of two separate, consecutive steps: ubiquitylation and proteasomal degradation. In particular, the ubiquitin proteasome system is the principal pathway for the clearance of short-lived, damaged, and mis-folded proteins in the nucleus and cytoplasm. The ubiquitin proteasome system controls the degradation...