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Molecular and Cellular Biology, April 1999, p. 2556-2566, Vol. 19, No. 4
Programme in Developmental Genetics, The
Babraham Institute, Cambridge CB2 4AT, United Kingdom
Received 11 November 1998/Returned for modification 30 December
1998/Accepted 12 January 1999
The mouse H19 gene is expressed from the maternal
chromosome exclusively. A 2-kb region at 2 to 4 kb upstream of
H19 is paternally methylated throughout development, and
these sequences are necessary for the imprinted expression of both
H19 and the 5'-neighboring Igf2 gene. In
particular, on the maternal chromosome this element appears to insulate
the Igf2 gene from enhancers located downstream of
H19. We analyzed the chromatin organization of this element by assaying its sensitivity to nucleases in nuclei. Six DNase I
hypersensitive sites (HS sites) were detected on the unmethylated maternal chromosome exclusively, the two most prominent of which mapped
2.25 and 2.75 kb 5' to the H19 transcription initiation site. Five of the maternal HS sites were present in expressing and
nonexpressing tissues and in embryonic stem (ES) cells. They seem,
therefore, to reflect the maternal origin of the chromosome rather than
the expression of H19. A sixth maternal HS site, at 3.45 kb
upstream of H19, was detected in ES cells only. The
nucleosomal organization of this element was analyzed in tissues and ES
cells by micrococcal nuclease digestion. Specifically on the maternal chromosome, an unusual and strong banding pattern was obtained, suggestive of a nonnucleosomal organization. From our studies, it
appears that the unusual chromatin organization with the presence of HS
sites (maternal chromosome) and DNA methylation (paternal chromosome)
in this element are mutually exclusive and reflect alternate epigenetic
states. In addition, our data suggest that nonhistone proteins are
associated with the maternal chromosome and that these might be
involved in its boundary function.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Parental Allele-Specific Chromatin Configuration in
a Boundary-Imprinting-Control Element Upstream of the Mouse
H19 Gene
*
Corresponding author. Mailing address: Programme in
Developmental Genetics, The Babraham Institute, Cambridge CB2 4AT,
United Kingdom. Phone: 44-1223-496332. Fax: 44-1223-496030. E-mail:
robert.feil{at}bbsrc.ac.uk.
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