Methods to induce proteasomal degradation of unwanted proteins are valuable in 
biomedical studies and thus receive increasing attention. For efficient 
degradation, the proteasome requires both a ubiquitin tag, which delivers 
substrates to the proteasome, and an unstructured region, where the proteasome 
engages the substrate for unfolding and degradation. We fused two degron 
components into a single molecule to create a fusion protein comprising 
ubiquitin and Rpn4-derived unstructured region. We demonstrated that the fusion 
protein retained its function to polyubiquitinate target proteins, thereby 
inducing more efficient proteasomal target degradation than wild-type ubiquitin 
in vitro and in cells. These results provide novel strategies for robust 
degradation enhancement of polyubiquitinated proteins.