Structural analysis of the human insulin-like growth factor-II P3 promoter

The expression of insulin-like growth factor-II (IGF-II) has been observed previously in many human cancers. The human IGF-II P3 promoter has been shown by others to give rise to abundant 6.0 kb and 2.2 kb fetal transcripts which are expressed in a variety of both paediatric and adult tumours. In order to determine the mechanism by which the P3 promoter is controlled, the promoter was analysed in cell lines using chloramphenicol acetyltransferase (CAT) assay and DNAase I footprinting techniques. The data indicated that P3 is a complex promoter involving at least nine transcription factor binding sites. Furthermore, high levels of 5-methylcytosine detected in the P3 promoter of HeLa genomic DNA suggest that IGF-II gene expression may also be influenced by DNA methylation.