Diagrams and expression of constructs designed to compare enhancing activity of the μLCR and HS3/HS2. (A) Is for constructs containing the ^Ag-globin gene (thin filled bars) with the −382 promoter and G → A transition at position −117, while (B) is for constructs containing the β-globin gene with the −267 promoter and no 3′ enhancer (thin open bars). Exons are indicated by the boxes, and the sites of transcription initiation (cap sites) are shown by the arrows. The μLCR is indicated by the thick hatched bar, while the HS3/HS2 enhancer core fragments are indicated by heavy and light stippling, respectively. To the right of each panel, the number of transfected MEL585 pools included in the analysis is shown along with the mean, standard deviation, and range of expression for each construct as described in the legend to Fig 1.