Human LCR γ-β globin gene constructs with γ promoter mutations and primer extension analysis of transgenic mouse RNA. (A) Human Aγ-globin gene promoter sequences from –202 to –130. The location of GATA(distal), Oct1, GATA(proximal) and CACCC box elements are marked above the sequence. (B) LCR γ-β constructs with GATA(distal), Oct1, GATA(proximal) and CACCC mutations in the human γ-globin gene promoter. (C) Primer extension analysis of 10.5 day yolk sac RNA (YS), 15.5 day fetal liver RNA (FL) and adult blood RNA (Bl) from transgenic mouse lines. The results demonstrate that the CACCC box of the human γ-globin gene promoter regulates β-globin gene developmental specificity.