Deletion analysis of γ-globin promoter-CAT fusion constructs in K562 after induction by butyrate, histone deacetylase inhibitors, or hydroxyurea. K562 cells were transfected (see Materials and Methods) with γ-globin promoter-CAT plasmids containing sequences from −1091 to +45 bp relative to the transcription start site with the indicated 5′ ends. The transfected cells were treated with arginine butyrate (, 1 mmol/L), trapoxin (▧, 2.5 nmol/L), trichostatin A (□, 100 nmol/L), or hydroxyurea (▨, 1 mmol/L) for 36 hours, then harvested and assayed for CAT activity. (▪), Untreated. The experiment shown is representative of three transfections done with the deletion series.