The barrier insulators recruit enzymatic activities like Histone acetyltransferase (HAT) that would hyperacetylate nearby histone proteins. This would in turn inhibit methylation of histones. The presence of su(var) gene encoding a methyltransferase that would add methyl group to specific amino acid residue in the tail of the H3 (Histone methyl transferase or HMTase). Chromatins that are modified in this way binds HP-1 proteins that are then associated to form heterochromatin. Thus, the heterochromatin promoting proteins are prevented from binding near the barrier insulator.