Identification of proximal cis-elements in GATA-1 promoter/enhancer region. (A) Parent construct DE1776 was generated by deleting a sequence between -4257 and -1775 of the GATA-1 promoter from plasmid G1-GM2. Other constructs were generated by deleting variable lengths of sequence between the distal control region and translation start codon. Deleted regions are indicated by the bold line. Primers P4967 and SP6 (arrowheads) were used to amplify the region in each construct required for microinjection (detailed in Materials and Methods). (B) The percentages of GFP-positive 48-hour embryos obtained after microinjection of these constructs are shown, with the number of embryos observed for each construct indicated in parentheses.