To examine the effects of PA28αβ silencing on mHTT(Q97) clearance in STHdh cells that express high PA28αβ levels, and thereby mimic the decrease in PA28αβ capped proteasomes observed in HD mice, we reduced PA28α levels by 80% using retroviral transduction of shRNA targeting PA28α (Fig 5A). The gene discussed is PSME1; the disease is Huntington disease.