Degradation of caspase-activated DNase by the ubiquitin–proteasome system

DNA fragmentation is one of the most characteristic features of apoptotic cells and caspase-activated DNase (CAD) is considered to be a major nuclease responsible for DNA fragmentation. CAD forms a complex with its inhibitor (ICAD), which is also required for the functional folding of CAD, leading to CAD stabilization in cells. In this paper, we investigated the involvement of the ubiquitin–proteasome system in CAD stability. The expression and ubiquitination of CAD was remarkably increased by MG132 treatment in the absence of ICAD. These results suggest that CAD protein may be preferentially degraded by the ubiquitin–proteasome system in the absence of ICAD to maintain protein quality control.