Recent data has implicated the Ski protein as being a physiologically relevant negative regulator of signaling by retinoic acid (RA). The mechanism by which Ski represses RA signaling is unknown. Co-immunoprecipitation and immunofluorescence assay showed that Ski and RAR alpha are in the same complex in both the absence and presence of RA, which makes Ski different from other corepressors. We determined that Ski can stabilize RAR alpha and HDAC3. These results suggest that Ski represses RA signaling by stabilizing corepressor complex. (C) 2009 Elsevier Inc. All rights reserved.