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Sequence‐specific positioning of nucleosomes over the steroid‐inducible MMTV promoter.
Author(s) -
RichardFoy H.,
Hager G. L.
Publication year - 1987
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1987.tb02507.x
Subject(s) - biology , carcinogenesis , chromatin , microbiology and biotechnology , cancer , gene , genetics
We have investigated chromatin organization over the MMTV LTR, a promoter regulated by steroid hormones. The studies were performed on cell lines containing BPV‐based episomal constructs. Nucleosome positioning was determined by localization of sites sensitive to the enzyme micrococcal nuclease, or to the chemical MPE‐Fe(II). Experiments with both reagents indicate that nucleosomes are specifically positioned in MMTV LTR chromatin. In the absence of hormone a regular cutting pattern is obtained, with cleavage sites at +136, −60, −250, −444, −651, −826 and −1019 relative to the Cap site. In the presence of hormone the cutting pattern is unchanged, except for a region between −60 and −250 that becomes hypersensitive to MPE‐Fe(II). This region contains the DNA sequences to which steroid receptor complexes bind during transcriptional activation. Our results indicate that this region is associated in chromatin from uninduced cells with a macromolecular complex (probably a nucleosome core), and this complex is displaced (or modified) upon binding of activated receptor.