The present invention features substantially pure HDAC9, HDAC9a, HDAC9(.DELTA.NLS), HDAC9a(.DELTA.NLS), an HDRP(.DELTA.NLS) polypeptides, and isolated nucleic acid molecules encoding those polypeptides. The present invention also features vectors containing HDAC9, HDAC9a, HDAC9(.DELTA.NLS), HDAC9a(.DELTA.NLS), and HDRP(.DELTA.NLS) nucleic acid sequences, and cells containing those vectors.