Department of Cellular Biochemistry and Human Genetics; The Hebrew University of Jerusalem Medical School
Using transient transfection experiments, we have determined the minimal promoter sequence of the mouse Snrpn gene. this sequence includes 84 bp upstream and the entire 79 bp exon 1. In the upstream region our experiments revealed a unique CpG site within a 7 bp element that is absolutely required for promoter activity. Methylation of this CpG site is sufficient to prevent the specific binding of a protein factor, and completely abolish promoter activity. The 3' half of exon 1 is also critical for promoter activity. The same 7 bp element is also present in the human SNRPN promoter. Surprisingly, the syntenic SNRPN promoter/exon 1 region did not show promoter activity. However, the human upstream region that contains the 7 bp element could support promoter activity, provided the 3' half of the human exon 1 was replaced with the corresponding mouse sequence. This minimal promoter sequence, being part of the presumed regional control mechanism that governs the imprinting of the entire PWS/AS 2 Mb region in mouse and human, raises the possibility that the elements that we have identified in the mouse, the 7 bp element and the 3' part of exon 1 play also a role in the regional control of the PWS/AS domain. Recent transient transgenic experiments that we are performing seem to support this possibility.