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Mol. Cell. Biol., 02 1997, 895-905, Vol 17, No. 2
AK Ostlund Farrants, P Blomquist, H Kwon and O Wrange
The organization of DNA in chromatin is involved in repressing basal
transcription of a number of inducible genes. Biochemically defined
multiprotein complexes such as SWI/SNF (J. Cote, J. Quinn, J. L. Workman,
and C. L. Peterson, Science 265:53-60, 1994) and nucleosome remodeling
factor (T. Tsukiyama and C. Wu, Cell 83:1011-1020, 1995) disrupt
nucleosomes in vitro and are thus candidates for complexes which cause
chromatin decondensation during gene induction. In this study we show that
the glucocorticoid receptor (GR), a hormone- inducible transcription
factor, stimulates the nucleosome-disrupting activity of the SWI/SNF
complex partially purified either from HeLa cells or from rat liver tissue.
This GR-mediated stimulation of SWI/SNF nucleosome disruption depended on
the presence of a glucocorticoid response element. The in
vitro-reconstituted nucleosome probes used in these experiments harbored 95
bp of synthetic DNA-bending sequence in order to rotationally position the
DNA. The GR-dependent stimulation of SWI/SNF-mediated nucleosome
disruption, as evaluated by DNase I footprinting, was 2.7- to 3.8-fold for
the human SWI/SNF complex and 2.5- to 3.2-fold for the rat SWI/SNF complex.
When nuclear factor 1 (NF1) was used instead of GR, there was no
stimulation of SWI/SNF activity in the presence of a mononucleosome
containing an NF1 binding site. On the other hand, the SWI/SNF nucleosome
disruption activity increased the access of NF1 for its nucleosomal binding
site. No such effect was seen on binding of GR to its response element. Our
results suggest that GR, but not NF1, is able to target the nucleosome-
disrupting activity of the SWI/SNF complex.
Copyright © 1997, American Society for Microbiology
Glucocorticoid receptor-glucocorticoid response element binding stimulates nucleosome disruption by the SWI/SNF complex
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, Stockholm, Sweden.
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