Fig. 1. Proteins interacting with the CCAAT box of the human β-globin gene. (A) Sequence of the CCAAT box with the contact sites of NFE-6 indicated by black circles. The imperfect dyad symmetric C/EBP binding site is shown by arrows. (B) Bandshift analysis of proteins binding to the β-globin CCAAT box. An oligonucleotide probe covering the CCAAT box was incubated with 4 µg of MEL cell nuclear extract plus the indicated antibodies; PI, pre-immune serum. Lanes 12–14 contain extracts from MEL cells overexpressing the indicated EBP proteins. (C) Constructs used to express C/EBPγ and C/EBPγΔB. Restriction sites used to isolate the microinjection fragments are indicated. (D) RT–PCR analysis of C/EBPγ expression in embryonic and fetal haematopoietic tissues. Two micrograms of RNA from the indicated tissues (bl, blood; ys, yolk sac, fl, fetal liver) were used for RT–PCR (30 cycles). No RT, reverse transcriptase was omitted to exclude amplification of contaminating DNA.