Aspartic protease. Required for the cleavage and activation of transcription factors such as isoform a of the transcription factor skn-1, which in turn regulates the expression of proteasomal subunits such as rpt-3. Mainly localizes to the nucleus during proteasomal disruption. Expressed in most tissues. Increased sensitivity to low doses of bortezomib which causes proteasome dysfunction. Double knockout with proteasomal subunit pbs-5 or with rpt-5 knockdown results in failed expression of the proteasomal subunit rpt-3. Double knockout with pbs-5 also results in the occasional mis-localization of the transcription factor skn-1a within gut nuclei. Belongs to the DDI1 family.