Enhancer-like activity of the DNA fragment encompassing the 3-bp deletion. (A) Enhancer-like activity of the 61-bp DNA fragment surrounding the 3-bp deletion polymorphism on HBG2 proximal promoter linked to a luciferase expression vector. The luciferase activity of the plasmid without the 61-bp DNA fragment was normalized to be 1.0. The 61-bp DNA fragment enhances the HBG2 promoter activity to 3.4-fold of the control. The 58-bp DNA fragment with the 3-bp deletion enhances the HBG2 promoter activity to 5.4-fold of the control. (B) Effect of mutation of transcription factor binding sites in the 61-bp DNA fragment on its enhancer-like activity. The luciferase activity of the plasmid with the 61-bp DNA fragment was normalized to be 1.0. Mutation of either RUNX1 or 3′ GATA binding site down-regulates the enhancer-like activity to 50%. Mutation of the E-box or 5′ GATA binding site does not decrease the enhancer-like activity of the DNA fragment. (C) Effect of mutation of transcription factor binding sites in the 58-bp DNA fragment with the 3-bp deletion on its enhancer-like activity. The luciferase activity of the plasmid with the 58-bp DNA fragment was normalized to be 1.0. Mutation of the E-box, RUNX1, or 3′ GATA binding site down-regulates the enhancer-like activity to approximately 50%. Mutation of the 5′ GATA binding site does not decrease the enhancer-like activity of the DNA fragment.