Transcriptional Repression of Human Insulin-Like Growth Factor-II P4 Promoter by Wilms' Tumor Suppressor WT1

The Wilms' tumor suppressor gene wt1 encodes a zinc Finger-containing protein that binds to the same DNA sequence as Egr-1, a mitogen-inducible immediate-early gene product that activates transcription. In this study, we investigated whether the human insulin-like growth factor-II (IGF-II) P4 promoter might be a target for transcriptional repression mediated by WT1. Using constructs of the IGF-II P4 promoter linked to the chloramphenicol acetyltransferase gene, we have demonstrated that the WT1 protein represses expression of the IGF-II gene through a GCGGGGGAG response element spanning nucleotides −87 to −65 of the IGF-II P4 promoter. Conversely, we have shown that the Egr-1 activates transcription of the IGF-II gene through the same response element. WT1 and Egr-1 proteins interact directly with the WTl/Egr-1 response element of the IGF-II promoter 4 in gel mobility-shift assays. These findings demonstrate the importance of the WTl/Egr-1 consensus element for the expression of the IGF-II gene in response to positive or negative transcription signals.