Interaction of the C/EBPs
with the –218/–82 sequence. (A)
Nuclear extracts from Hep3B or A6 cells, which had been transfected
with the control pCS2+ vector (con) or the xC/EBPα expression plasmid (α-tran)
were used for EMSA with radiolabelled wt-C/EBP or NF-1
binding site oligonucleotides. (B) Competition
experiments were carried out using extracts from Hep3B cells transfected
with the xC/EBPα expression
plasmid and a 400-fold molar excess of oligonucleotides for: the
corresponding unlabelled wt-C/EBP sequence (+wt-C/EBP),
a C/EBP binding site from the C-reactive protein gene promoter
(+CRP), a C/EBP binding site from the β-cas
gene promoter (+β-cas), a NF-1
recognition sequence (+NF1) and a Sp1 binding site (+SP1).
(C) Antibody interference EMSA was carried out
using extracts from Hep3B cells transfected with the xC/EBPα expression plasmid and radiolabelled
wt-C/EBP or D-C/EBP oligonucleotides, in the absence
(α-tran) or the presence of antisera
against C/EBPα (+α) or C/EBPβ (+β), or pre-immune serum (PI). For EMSA
with wt-C/EBP oligonucleotide in (C), competition experiments
were also carried out using a 100- and 500-fold molar excess of
unlabelled D-C/EBP oligonucleotide (+D-C/EBP).
Vertical arrows labelled B, ss and F indicate the position of the
major DNA–protein complexes, antibody–DNA–protein
supershifted complexes and free probe, respectively. P represents
the profile obtained using the radiolabelled oligonucleotide alone;
the free probe in (A) and (B) has migrated from the gel.