Journal of Lipid Research, Vol 32, 137-145, Copyright © 1991 by Lipid Research, Inc.
A polymorphism in a region with enhancer activity in the second intron of the human apolipoprotein B gene
B Levy-Wilson, L Soria, EH Ludwig, M Argyres, AR Brooks, BD Blackhart, W Friedl and BJ McCarthy
Gladstone Foundation Laboratories for Cardiovascular Disease, Department of Pharmaceutical Chemistry, University of California, San Francisco 94140-0608.
A 443-base pair fragment (+622 to +1064) from the second intron of the
human apolipoprotein B gene was shown to contain a tissue-specific enhancer
when placed in front of an apolipoprotein B promoter- chloramphenicol
acetyltransferase construct in transfection experiments. To identify
potential regulatory mutations in this region of the gene, DNA from various
subjects was examined for the presence of point mutations by means of
chemical cleavage of mismatched heteroduplexes. An A----G substitution
within the second intron of the gene at position +722 was identified in
three unrelated subjects and confirmed by DNA sequencing. Although the base
substitution was contained within a nuclear protein-binding site, as
determined by DNase I footprinting, it did not appear to affect the
protein/DNA interaction in its vicinity, as shown by gel retardation
experiments. The single base substitution at position +722 abolishes a StyI
restriction site, thus creating a StyI polymorphism. Using allele-specific
oligonucleotides, we screened the DNA of 172 subjects for the presence of
this polymorphism: two other subjects carrying the polymorphism were found.
In each of the five unrelated subjects, the polymorphism was associated
with the same haplotype.
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