Open AccessSp1 sites in the mouse aprt gene promoter are required to prevent methylation of the CpG island.
Author(s) -
Donald Macleod,
Jillian Charlton,
John J. Mullins,
Adrian Bird
Publication year - 1994
Publication title -
genes and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.136
H-Index - 438
eISSN - 1549-5477
pISSN - 0890-9369
DOI - 10.1101/gad.8.19.2282
Subject(s) - biology , cpg site , methylation , adenine phosphoribosyltransferase , dna methylation , genetics , gene , illumina methylation assay , microbiology and biotechnology , differentially methylated regions , housekeeping gene , gene expression , biochemistry , purine , enzyme
In an attempt to find the mechanism by which CpG islands remain free of methylation we have undertaken a detailed examination of the mouse adenine phosphoribosyltransferase (aprt) gene. This housekeeping gene has a CpG island that extends over the gene promoter and includes the first two exons. We show that the island is free of methylation at all CpGs, whereas the flanks are methyated. Detailed patterns of methylation beyond the boundaries of the CpG island vary between cells. In vivo footprinting across the island region shows that three GC boxes clustered at the 5' edge of the CpG island are occupied, most probably by Sp1. No other footprints are detected within the island region. Deletion or mutagenesis of the Sp1 sites causes de novo methylation of the CpG island in a transgenic mouse assay. Thus, the peripherally located Sp1 sites are necessary to keep the aprt island methylation free.