ODC is the most well-characterized cellular protein subject to ubiquitin-independent proteasomal degradation.
Until a report by Sheaff et al. (2000),[REF] which demonstrated that the cyclin-dependent kinase (Cdk) inhibitor p21Cip1 is also degraded by the proteasome in a ubiquitin-independent manner, ODC was the only clear example of ubiquitin-independent proteasomal degradation [REF].