Project description:We exogenously expressed the SWI/SNF ATPase catalytic subunits BRG1 and BRM in the lacking cell line C33A, and compared the differences with mock transfected cell at gene expression and alternative splicing level.
Project description:SWI/SNF chromatin remodeling complexes control gene expression by regulating chromatin structure. However, the full subunit composition of SWI/SNF complexes in plants remains unclear. Here we show that BRAHMA Interacting Protein 1 (BRIP1) and BRIP2 in Arabidopsis thaliana are core subunits of plant SWI/SNF complexes. BRIP1 and 2 are two homolog proteins. brip1 brip2 double mutants exhibit developmental phenotypes and a transcriptome strikingly similar to those of BRAHMA (BRM) mutants. Genetic interaction tests indicated that BRIP1 and 2 act together with BRM to regulate gene expression. Furthermore, BRIP1 and 2 physically interact with BRM-containing SWI/SNF complexes, and extensively co-localize with BRM at endogenous genes. Loss-of-brip1brip2 results in decreased BRM occupancy at almost all BRM target genes and substantially reduced subunits incorporation into the BRM-containing SWI/SNF complexes. Together, our work identifies new core subunits of BRM-containing SWI/SNF complexes in plants, and uncovers the essential role of these subunits in regulating the integrity (assembly) of SWI/SNF complexes in plants.
Project description:Tissue-specific transcription factors initiate differentiation toward a specialized cell type by inducing transcription-permissive chromatin modifications at target gene promoters, through the recruitment of the SWI/SNF chromatin-remodeling complex (1, 2). The molecular mechanism that regulates the chromatin re-distribution of SWI/SNF in response to differentiation signals is currently unknown. Here we show that the muscle determination factor MyoD and the SWI/SNF structural sub-unit, BAF60c (SMARCD3), form a complex on the regulatory elements of MyoD-target genes in undifferentiated myoblasts, prior to the activation of gene expression. MyoD-BAF60c complex is devoid of the ATP-dependent enzymatic sub-units Brg1 and Brm, is required for stable MyoD binding to Ebox sequences, and marks the chromatin for signal-dependent recruitment of the SWI/SNF core complex to muscle loci. BAF60c phosphorylation on a conserved threonine by differentiation-activated p38 signalling promotes the incorporation of MyoD-BAF60c into a Brg1-based SWI/SNF complex, which is competent to remodel the chromatin and activates transcription of MyoD-target genes. Our data support an unprecedented two-step model, by which pre-assembled BAF60c-MyoD complex directs the SWI/SNF complex chromatin re-distribution to muscle loci in response to differentiation cues. Differentiation of C2C12 cells individually interfered for BRG1, BAF60B, BAF60C
Project description:The SWI/SNF complex remodels chromatin in an ATP-dependent manner through the ATPase subunits BRG1 and BRM. Chromatin remodeling alters nucleosome structure to change gene expression, however aberrant remodeling and gene expression can result in cancer. The function and localization on chromatin of the SWI/SNF complex depends on the protein makeup of the complex. Here we report the protein-protein interactions of wild-type BRG1 or mutant BRG1 in which the HSA domain has been deleted (BRG1-HSA). We demonstrate the interaction of BRG1 with most SWI/SNF complex members and a failure of a number of these members to interact with BRG1-HSA. These results demonstrate that the HSA domain of BRG1 is a critical interaction platform for the correct formation of SWI/SNF remodeling complexes.
Project description:The composition of chromatin remodeling complexes dictates how these enzymes control transcriptional programs and cellular identity. Here, we investigate 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 identify Brd7 as a novel component of the PBAF complex in both ESCs and differentiated cells. Using shRNA-mediated depletion of Brg1, we show 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 TRH. Knock-down studies of PBAF-specific Brd7 and of a signature subunit within the BAF complex, ARID1A, show that these two sub-complexes affect SWI/SNF target genes differentially, in some cases even antagonistically. This may be due to their different biochemical properties. Finally, we examine the role of SWI/SNF in regulating its target genes during differentiation. We find that SWI/SNF affects recruitment of components of the pre-initiation 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. R1 ESCs were infected in duplicates with shRNA targeting Brg1 or GLUT4 (as a control). Knockdown of Brg1 mRNA affected Brg1 protein levels efficiently. RNA was isolated 67 hours post-infection and analyzed using microarrays.
Project description:We monitored changes to genomic binding of BRG1 andBRM following BRG1 or BRM loss to understand how disuprtion of one member of the SWI/SNF complex affected remaining forms of the complex present in the cell.
Project description:Switch defective/sucrose non-fermentable chromatin remodeling complexes are multi-subunit machines that play vital roles in regulating chromatin structure and gene expression. However, how SWI/SNF complexes recognize target loci is still not fully understood. Here, we show that Arabidopsis bromodomain-containing homologous proteins, BRD1, BRD2 and BRD13, are core subunits of SWI/SNF complexes that are required for SWI/SNF genomic targeting. The three BRDs directly interact with multiple SWI/SNF subunits, including the BRAHMA (BRM) catalytic subunit. Phenotypic and transcriptome analysis of the brd1 brd2 brd13 triple mutants showed that the BRDs act in large redundancy to control developmental processes and gene expression that are also regulated by BRM. BRDs extensively co-localize with BRM on chromatin. brd1 brd2 brd13 mutation results in the reduced BRM protein levels and genome-wide targeting on chromatin. Finally, we demonstrate that the bromodomain of BRD2 is essential for genomic targeting of BRD2, highlighting the role of this reader domain in the recruitment of BRM-containing SWI/SNF complexes to target sites in plants. SWI/SNF chromatin remodeling complexes are evolutionarily conserved and is confirmed to use the energy derived from hydrolysis of ATP to alter the density or the position of nucleosomes on the DNA or the composition of histone octamer. Bromodomain, an acetylated histone interaction module, was found in chromatin remodeling factors. During the 29 Arabidopsis bromodomain-containing protein, like GCN5 and GTE4/6, their function has been reported. Here, we reported three BRM-interacting bromodomain-containing protein, BRD1, BRD2 and BRD13 are new core subunits of Arabidopsis SWI/SNF complexes. brd1/2/13 displayed a similar phenotype like brm, such as down-ward curled leaves, reduced fertility, shorter silique and root. Moreover, brm brd1/2/13 shows more serious phenotype just like brm-1. Y2H, Co-IP, RNA-seq and ChIP-seq assay reveal that BRDs interact with BRM at both protein and chromatin level. Future more, BRDs are required for BRM genome-wide occupancy and BRM might bind to chromatin via BRDs bromodomain by interacting with their BBC domain.
Project description:For cells to initiate and sustain a differentiated state, it is necessary that a “memory” of this state is transmitted through mitosis to the daughter cells. Mammalian SWItch/ Sucrose Non- Fermentable (SWI/SNF) complexes, also called Brg1/ Brg- associated factors (BAF), control cell identity by modulating chromatin architecture to regulate gene expression, but whether they participate in cell fate memory is unclear. Here, we provide evidence that subunits of SWI/SNF act as mitotic bookmarks to safeguard cell identity during cell division. The SWI/SNF core subunits SMARCE1 and SMARCB1 are displaced from enhancers but bound on promoters during mitosis and we show that this binding is required for appropriate reactivation of bound genes after mitotic exit. Ablation of SMARCE1 during a single mitosis in mouse embryonic stem cells is sufficient to disrupt gene expression, impair the occupancy of several established bookmarks at a subset of their targets, and cause aberrant neural differentiation. Thus, SWI/SNF subunit SMARCE1 plays a mitotic bookmarking role and is essential for heritable epigenetic fidelity during transcriptional reprogramming.