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Fig. 6. The overlapping CArG-like and YY1 sites are required for strong and
restricted expression of the XMLC2 promoter in the heart. (A) A binding
activity present in tadpole extracts binds the combined CArG-like/YY1 site in
proximal XMLC2 promoter (–122/–85). This activity (arrow) was
identified as YY1 as it is blocked by a specific antiserum to YY1, but not by
anti-SRF antibodies. The same complex is specifically competed by an
unlabelled YY1 site, but not by SP1 or GATA sites. (Ab, antibody; Fold, fold
molar excess of competitor; wt, unlabelled probe). (B,C) Mutation of theYY1
site alone (B) or in combination with the CArG-like/YY1 site (C) results in
variable (though generally weaker) and less uniform expression of GFP in the
heart (arrowhead), as well as in ectopic expression (arrows). Comparison of
the two panels indicates the variability in expression obtained with these
mutations. (D) The sequence of CArG-like/YY1 site and mutated versions tested
by transgenesis (see Table 1).
The YY1 motif in the wild-type sequence is underlined; mutated residues are
shown in red.
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