BRD7, a novel PBAF-specific SWI/SNF subunit, is required for target gene activation and repression in embryonic stem cells.
The composition of chromatin-remodeling complexes dictates how these enzymes control transcriptional programs and cellular identity. In the present study we investigated the composition of SWI/SNF complexes in embryonic stem cells (ESCs). In contrast to differentiated cells, ESCs have a biased incorporation of certain paralogous SWI/SNF subunits with low levels of ... BRM, BAF170, and ARID1B. Upon differentiation, the expression of these subunits increases, resulting in a higher diversity of compositionally distinct SWI/SNF enzymes. We also identified BRD7 as a novel component of the Polybromo-associated BRG1-associated factor (PBAF) complex in both ESCs and differentiated cells. Using short hairpin RNA-mediated depletion of BRG1, we showed that SWI/SNF can function as both a repressor and an activator in pluripotent cells, regulating expression of developmental modifiers and signaling components such as Nodal, ADAMTS1, BMI-1, CRABP1, and thyroid releasing hormone. Knockdown studies of PBAF-specific BRD7 and of a signature subunit within the BAF complex, ARID1A, showed that these two subcomplexes affect SWI/SNF target genes differentially, in some cases even antagonistically. This may be due to their different biochemical properties. Finally we examined the role of SWI/SNF in regulating its target genes during differentiation. We found that SWI/SNF affects recruitment of components of the preinitiation complex in a promoter-specific manner to modulate transcription positively or negatively. Taken together, our results provide insight into the function of compositionally diverse SWI/SNF enzymes that underlie their inherent gene-specific mode of action.
Mesh Terms:
Animals, Cell Cycle, Cell Differentiation, Chromosomal Proteins, Non-Histone, DNA Helicases, Embryonic Stem Cells, Gene Expression Regulation, Developmental, Humans, Mice, Models, Biological, Multiprotein Complexes, Nuclear Proteins, Transcription Factors, Transcription, Genetic
Animals, Cell Cycle, Cell Differentiation, Chromosomal Proteins, Non-Histone, DNA Helicases, Embryonic Stem Cells, Gene Expression Regulation, Developmental, Humans, Mice, Models, Biological, Multiprotein Complexes, Nuclear Proteins, Transcription Factors, Transcription, Genetic
J. Biol. Chem.
Date: Nov. 21, 2008
PubMed ID: 18809673
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