The KCNQ1OT1 promoter, a key regulator of genomic imprinting in human chromosome 11p15.5.

The human 11p15.5 region contains several maternally and paternally imprinted genes. Dysregulation of imprinting of some of these genes occurs in the Beckwith-Wiedemann syndrome and several tumors. Imprinting in this region is controlled by two imprinting control regions (ICR). ICR1 acts as an insulator that regulates the reciprocal imprinting of the IGF2 and H19 genes. A differentially methylated region in ICR2 regulates the expression of a long transcript called KCNQ1OT1. This paternally expressed transcript negatively regulates several paternally imprinted genes around ICR2. Biallelic expression of the KCNQ1OT1 transcript is the primary molecular defect in over 50% of cases of Beckwith-Wiedemann syndrome. To understand the role of KCNQ1OT1 in regulating ICR2 we characterized its promoter. The critical promoter is approximately 300 bp and it is surrounded by inhibitory elements within the CpG island. The promoter activity is strongly inhibited by cytosine methylation in keeping with the finding that the inactive maternal promoter is methylated in vivo. We have identified the transcription start sites and four CCAAT boxes upstream of the 5'-most start site. Mutation of the CCAAT boxes produced impairment of promoter activity. Transfection and gel mobility shift experiments suggest that binding of the factor NF-Y to the CCAAT boxes is important for promoter activity.