Expression levels (average values and standard deviations of triplicate determinations) normalized to housekeeping genes such as GAPDH and ??-ACTIN were calculated using a standard curve and the relative quantification method as described in ABI User Bulletin #2.Chromatin immunoprecipitation assayChromatin immunoprecipitations were performed as previously described (Weinmann and Farnham, 2002; Yok