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Glucocorticoid receptor-glucocorticoid response element binding stimulates nucleosome disruption by the SWI/SNF complex.

ABSTRACT: 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. Côté, 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.

SUBMITTER: Ostlund Farrants AK

PROVIDER: S-EPMC231816 | biostudies-other | 1997 Feb

REPOSITORIES: biostudies-other

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Glucocorticoid receptor-glucocorticoid response element binding stimulates nucleosome disruption by the SWI/SNF complex.

Ostlund Farrants A K AK Blomquist P P Kwon H H Wrange O O

Molecular and cellular biology 19970201 2

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. Côté, 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 glu ...[more]

PMID: 9001244

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Project description:BackgroundGlucocorticoids are used in the curative treatment of acute lymphoblastic leukemia (ALL). Resistance to glucocorticoids is an important adverse prognostic factor in newly diagnosed ALL patients but its mechanism is unknown. Because SWI/SNF complex-mediated chromatin remodeling is required for glucocorticoid transcriptional activity in vitro, we investigated whether expression of subunits of the SWI/SNF complex was related to glucocorticoid resistance in ALL.MethodsGene expression and in vitro sensitivity to prednisolone and dexamethasone were assessed in a training set of primary ALL cells from 177 children with newly diagnosed ALL and a validation set of cells from an independent cohort of 95 ALL patients. The global test method was used to select pathways whose genes were associated with drug sensitivity. Genes involved in chromatin remodeling were identified by use of the Gene Ontology database. Short hairpin RNA (shRNA) was used to knock down mRNA expression of SMARCA4 in glucocorticoid-sensitive Jurkat human ALL cells. Spearman rank correlation, multiple linear regression, and logistic regression were used to investigate associations between gene expression and glucocorticoid sensitivity. All statistical tests were two-sided.ResultsStatistically significant associations between decreased expression in ALL cells of genes for core subunits of the SWI/SNF complex-SMARCA4, ARID1A, and SMARCB1-and resistance to prednisolone and dexamethasone were identified in the training cohort. In the validation cohort, expression of SMARCA4 (P < .001 and r = -0.43), ARID1A (P = .016 and r = -0.29), and SMARCB1 (P = .019 and r = -0.29) in ALL cells was statistically significantly associated with dexamethasone sensitivity, and SMARCA4 expression (P = .018 and r = -0.28) was statistically significantly associated with prednisolone sensitivity. Prednisolone resistance was higher in SMARCA4 shRNA-transfected Jurkat cells (drug concentration lethal to 50% of the leukemia cells [LC(50)] = 277 microM) than in control shRNA-transfected cells (LC(50) = 174 microM, difference = 103 microM, 95% confidence interval of the difference = 100 to 106 microM; P < .001, t test).ConclusionDecreased expression of as many as three subunits of the SWI/SNF complex appears to be associated with glucocorticoid resistance in primary ALL cells.

Dataset Information

Glucocorticoid receptor-glucocorticoid response element binding stimulates nucleosome disruption by the SWI/SNF complex.

Publications

Glucocorticoid receptor-glucocorticoid response element binding stimulates nucleosome disruption by the SWI/SNF complex.

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