Abstract
The P3 promoter of the human insulin-like growth factor II (IGF-II) is the major
IGF-II promoter in fetal liver (FL) and hepatocellular carcinoma (HCC). However,
little information is available on the transcriptional factors (TFs) controlling
IGF-II gene expression in human liver cirrhosis (LC) and HCC tissues. To
evaluate the protein-binding patterns in the P3 promoter region, we performed
electromobility shift assay (EMSA) and DNase I footprinting assay using nuclear
extracts from human FL, LC and HCC tissues. EMSA showed considerable differences
in binding patterns of proteins to P3 promoter region according to different
nuclear extracts used in this study. By footprinting assay, eight footprints
were observed in extracts. In addition, LC extract showed two specific binding
at L1 [-80:+30] and L2 [-126:-80] regions, and HCC showed two specific binding
at H1 [-176:-120] and H2 [-210:-177] as well as two liver specific binding (L1
and L2). Footprinting after immunoprecipitation indicates that Egr1, Egr2 and
Sp1 could bind to P3 promoter directly, while c-jun and c-fos could not bind to
these region directly. Further study is required to determine the function of
these proteins.