FIG. 1.

(A) Schematic representation of the chicken α-globin domain with regulatory and structural elements. Globin genes and regions of homology with exons of the human gene “-14” are shown by filled rectangles. The open rectangle shows the position of the CpG island (33), which includes a weak enhancer (34) and an origin of bidirectional DNA replication (35, 45). Directions of replication are shown below by horizontal arrows. The filled triangle shows the position of a strong erythroid cell-specific enhancer (25) and silencer (38). DNase I-hypersensitive sites (DHs) are shown by arrows (15, 20, 31, 43); closed arrows represent erythroid cell-specific DHs; thin arrows show DHs in promoter regions; open arrows show constitutive DHs. (B) The putative CTCF-binding site (50 bp) located within the 200-bp SmaI fragment. The arrow indicates the direction of ggPRX gene transcription. The regions critical for CTCF binding deduced from alignment of the putative CTCF-binding site with the FII sequence (CTCF) recognition site from the chicken β-globin domain 5′ HS4 insulator (2) are shown in boldface type. The numbers defining the two SmaI sites correspond to GenBank sequence AF098919, and the numbers in brackets show their positions relative to the start of π gene transcription.