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Molecular and Cellular Biology, November 1998, p. 6767-6776, Vol. 18, No. 11
Division of Biology, Beckman Research
Institute of the City of Hope, Duarte, California 91010
Received 11 May 1998/Returned for modification 22 June
1998/Accepted 7 August 1998
Genomic imprinting results in parent-specific monoallelic
expression of a small number of genes in mammals. The identity of imprints is unknown, but much evidence points to a role for DNA methylation. The maternal alleles of the imprinted H19 gene
are active and hypomethylated; the paternal alleles are inactive and hypermethylated. Roles for other epigenetic modifications are suggested
by allele-specific differences in nuclease hypersensitivity at
particular sites. To further analyze the possible epigenetic mechanisms
determining monoallelic expression of H19, we have conducted in vivo dimethylsulfate and DNase I footprinting of regions
upstream of the coding sequence in parthenogenetic and androgenetic
embryonic stem cells. These cells carry only maternally and paternally
derived alleles, respectively. We observed the presence of
maternal-allele-specific dimethylsulfate and DNase I footprints at the
promoter indicative of protein-DNA interactions at a CCAAT box and at
binding sites for transcription factors Sp1 and AP-2. Also, at the
boundary of a region further upstream for which existent differential
methylation has been suggested to constitute an imprint, we observed a
number of strand-specific dimethylsulfate reactivity differences
specific to the maternal allele, along with an unusual chromatin
structure in that both strands of maternally derived DNA were strongly
hypersensitive to DNase I cutting over a distance of 100 nucleotides.
We therefore reveal the existence of novel parent-specific epigenetic
modifications, which in addition to DNA methylation, could constitute
imprints or maintain monoallelic expression of H19.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Characterization of Novel Parent-Specific Epigenetic
Modifications Upstream of the Imprinted Mouse H19
Gene
*
Corresponding author. Mailing address: Division of
Biology, Beckman Research Institute of the City of Hope, 1450 East
Duarte Road, Duarte CA 91010. Phone: (626) 301-8813. Fax: (626)
358-7703. E-mail: jmann{at}nwc.net.
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