ABSTRACT: ANGUSTIFOLIA 3 binds Arabidopsis SWI/SNF chromatin remodeling complexes to regulate transcription at the switch from leaf cell proliferation to expansion
Project description:The transcriptional coactivator ANGUSTIFOLIA 3 (AN3) stimulates cell proliferation during Arabidopsis leaf development, but the molecular mechanism is largely unknown. We show here that inducible nuclear localization of AN3 during initial leaf growth results in differential expression of important transcriptional regulators, including GROWTH REGULATING FACTORs (GRFs). Chromatin purification further revealed the presence of AN3 at the loci of GRF5, GRF6, CYTOKININ RESPONSE FACTOR 2 (CRF2), CONSTANS-LIKE 5 (COL5), HECATE 1 (HEC1), and ARABIDOPSIS RESPONSE REGULATOR 4 (ARR4). Tandem affinity purification of protein complexes using AN3 as bait identified plant SWITCH/SUCROSE NONFERMENTING (SWI/SNF) chromatin remodeling complexes formed around the ATPases BRAHMA (BRM) or SPLAYED (SYD). Moreover, SWI/SNF ASSOCIATED PROTEIN 73B (SWP73B) is recruited by AN3 to the promoter of GRF5, GRF3, COL5, and ARR4, and both SWP73B and BRM occupy the HEC1 promoter. Furthermore, we show that AN3 and BRM genetically interact. The data indicate that AN3 associates with chromatin remodelers to regulate transcription. In addition, modification of SWI3C expression levels increases leaf size, underlining the importance of chromatin dynamics for growth regulation. Our results place the SWI/SNF-AN3 module as a major player at the transition from cell proliferation to cell differentiation in a developing leaf. AN3-GR and wild-type (Col-0) plants were grown in vitro for 8 days and subsequently transferred to dexamethasone-containing medium for 8 hours. Developing leaves 1&2 of AN3-GR and wild-type plants were micro-dissected, and RNA was extracted. RNA from three biological repeats of dexamethasone-treated AN3-GR and dexamethasone-treated wild-type leaves was hybridized to Affymetrix ATH1 microarrays.
Project description:The transcriptional coactivator ANGUSTIFOLIA 3 (AN3) stimulates cell proliferation during Arabidopsis leaf development, but the molecular mechanism is largely unknown. We show here that inducible nuclear localization of AN3 during initial leaf growth results in differential expression of important transcriptional regulators, including GROWTH REGULATING FACTORs (GRFs). Chromatin purification further revealed the presence of AN3 at the loci of GRF5, GRF6, CYTOKININ RESPONSE FACTOR 2 (CRF2), CONSTANS-LIKE 5 (COL5), HECATE 1 (HEC1), and ARABIDOPSIS RESPONSE REGULATOR 4 (ARR4). Tandem affinity purification of protein complexes using AN3 as bait identified plant SWITCH/SUCROSE NONFERMENTING (SWI/SNF) chromatin remodeling complexes formed around the ATPases BRAHMA (BRM) or SPLAYED (SYD). Moreover, SWI/SNF ASSOCIATED PROTEIN 73B (SWP73B) is recruited by AN3 to the promoter of GRF5, GRF3, COL5, and ARR4, and both SWP73B and BRM occupy the HEC1 promoter. Furthermore, we show that AN3 and BRM genetically interact. The data indicate that AN3 associates with chromatin remodelers to regulate transcription. In addition, modification of SWI3C expression levels increases leaf size, underlining the importance of chromatin dynamics for growth regulation. Our results place the SWI/SNF-AN3 module as a major player at the transition from cell proliferation to cell differentiation in a developing leaf.
Project description:Switch defective/sucrose non-fermentable (SWI/SNF) chromatin remodeling complexes are multi-subunit machineries that establish and maintain chromatin accessibility and gene expression by regulating chromatin structure. However, how the remodeling activities of SWI/SNF complexes are regulated in eukaryotes remains elusive. B-cell lymphoma/leukemia protein 7A/B/C (BCL7A/B/C) have been reported as subunits of SWI/SNF complexes for decades in animals and recently in plants; however, the role of BCL7 subunits in SWI/SNF function remains undefined. Here, we identify a unique role for plant BCL7A and BCL7B homologous subunits in potentiating the genome-wide chromatin remodeling activities of BRAHMA-SWI/SNF complexes in plants. BCL7A/B require the catalytic ATPase BRAHMA (BRM) to assemble with the signature subunits of the BRM-SWI/SNF complexes and for genomic binding at a subset of target genes. Loss of BCL7A and BCL7B diminishes BRM-mediated genome-wide chromatin accessibility without changing the stability and genomic targeting of the BRM-SWI/SNF complex, highlighting the specialized role of BCL7A/B in regulating remodeling activity. We further show that BCL7A/B fine-tunes the remodeling activity of BRM-SWI/SNF complexes to generate accessible chromatin at the juvenility resetting region (JRR) of the microRNAs MIR156A/C for plant juvenile identity maintenance. In summary, our work uncovers the function of previously elusive SWI/SNF subunits in multicellular eukaryotes and provides insights into the mechanisms whereby plants memorize the juvenile identity through SWI/SNF-mediated control of chromatin accessibility.
Project description:Switch defective/sucrose non-fermentable (SWI/SNF) chromatin remodeling complexes are multi-subunit machineries that establish and maintain chromatin accessibility and gene expression by regulating chromatin structure. However, how the remodeling activities of SWI/SNF complexes are regulated in eukaryotes remains elusive. B-cell lymphoma/leukemia protein 7A/B/C (BCL7A/B/C) have been reported as subunits of SWI/SNF complexes for decades in animals and recently in plants; however, the role of BCL7 subunits in SWI/SNF function remains undefined. Here, we identify a unique role for plant BCL7A and BCL7B homologous subunits in potentiating the genome-wide chromatin remodeling activities of BRAHMA-SWI/SNF complexes in plants. BCL7A/B require the catalytic ATPase BRAHMA (BRM) to assemble with the signature subunits of the BRM-SWI/SNF complexes and for genomic binding at a subset of target genes. Loss of BCL7A and BCL7B diminishes BRM-mediated genome-wide chromatin accessibility without changing the stability and genomic targeting of the BRM-SWI/SNF complex, highlighting the specialized role of BCL7A/B in regulating remodeling activity. We further show that BCL7A/B fine-tunes the remodeling activity of BRM-SWI/SNF complexes to generate accessible chromatin at the juvenility resetting region (JRR) of the microRNAs MIR156A/C for plant juvenile identity maintenance. In summary, our work uncovers the function of previously elusive SWI/SNF subunits in multicellular eukaryotes and provides insights into the mechanisms whereby plants memorize the juvenile identity through SWI/SNF-mediated control of chromatin accessibility.
Project description:Cilia are important subcellular organelles and are regulated by transcription factors including Foxj1 and Rfx proteins. Whether and how are cilia regulated at epigenetic level remains unknown. We addressed this question by knocking down or knocking out of chromatin remodeling genes. Interestingly, depletion of multiple components of the switch/sucrose non-fermentable (SWI/SNF) complexes lead to ciliopathy-like phenotypes in zebrafish embryos. Specifically, depletion of Actl6a, one of the components of the SWI/SNF complexes lead cilia disassembly and cystic kidney, but do not affect cilia motility. Omics studies show that in Actl6a-depleted embryos, a set of cilia genes including Foxj1a and Rfx2, the master regulators of cilia assembly, were downregulated at transcriptional level, chromatin accessibility and the SWI/SNF complexes binding. Thus, our study reveals that the SWI/SNF complexes regulate cilia stability and kidney development by direct modulating the expression Foxj1a and Rfx2.
Project description:Cilia are important subcellular organelles and are regulated by transcription factors including Foxj1 and Rfx proteins. Whether and how are cilia regulated at epigenetic level remains unknown. We addressed this question by knocking down or knocking out of chromatin remodeling genes. Interestingly, depletion of multiple components of the switch/sucrose non-fermentable (SWI/SNF) complexes lead to ciliopathy-like phenotypes in zebrafish embryos. Specifically, depletion of Actl6a, one of the components of the SWI/SNF complexes lead cilia disassembly and cystic kidney, but do not affect cilia motility. Omics studies show that in Actl6a-depleted embryos, a set of cilia genes including Foxj1a and Rfx2, the master regulators of cilia assembly, were downregulated at transcriptional level, chromatin accessibility and the SWI/SNF complexes binding. Thus, our study reveals that the SWI/SNF complexes regulate cilia stability and kidney development by direct modulating the expression Foxj1a and Rfx2.
Project description:Cilia are important subcellular organelles and are regulated by transcription factors including Foxj1 and Rfx proteins. Whether and how are cilia regulated at epigenetic level remains unknown. We addressed this question by knocking down or knocking out of chromatin remodeling genes. Interestingly, depletion of multiple components of the switch/sucrose non-fermentable (SWI/SNF) complexes lead to ciliopathy-like phenotypes in zebrafish embryos. Specifically, depletion of Actl6a, one of the components of the SWI/SNF complexes lead cilia disassembly and cystic kidney, but do not affect cilia motility. Omics studies show that in Actl6a-depleted embryos, a set of cilia genes including Foxj1a and Rfx2, the master regulators of cilia assembly, were downregulated at transcriptional level, chromatin accessibility and the SWI/SNF complexes binding. Thus, our study reveals that the SWI/SNF complexes regulate cilia stability and kidney development by direct modulating the expression Foxj1a and Rfx2.
Project description:Cilia are important subcellular organelles and are regulated by transcription factors including Foxj1 and Rfx proteins. Whether and how are cilia regulated at epigenetic level remains unknown. We addressed this question by knocking down or knocking out of chromatin remodeling genes. Interestingly, depletion of multiple components of the switch/sucrose non-fermentable (SWI/SNF) complexes lead to ciliopathy-like phenotypes in zebrafish embryos. Specifically, depletion of Actl6a, one of the components of the SWI/SNF complexes lead cilia disassembly and cystic kidney, but do not affect cilia motility. Omics studies show that in Actl6a-depleted embryos, a set of cilia genes including Foxj1a and Rfx2, the master regulators of cilia assembly, were downregulated at transcriptional level, chromatin accessibility and the SWI/SNF complexes binding. Thus, our study reveals that the SWI/SNF complexes regulate cilia stability and kidney development by direct modulating the expression Foxj1a and Rfx2.
Project description:SWI/SNF chromatin remodeling complexes play critical roles in transcription and other chromatin-related processes. The analysis of the two members of this class in Saccharomyces cerevisiae, SWI/SNF and RSC, has heavily contributed to our understanding of these complexes. To understand the in vivo functions of SWI/SNF and RSC in an evolutionarily distant organism, we have characterized these complexes in Schizosaccharomyces pombe. While core components are conserved between the two yeasts, the compositions of S. pombe SWI/SNF and RSC differ from their S. cerevisiae counterparts and in some ways are more similar to metazoan complexes. Furthermore, several of the conserved proteins, including actin-like proteins, are strikingly different between the two yeasts with respect to their requirement for viability. Finally, phenotypic and microarray analyses identified widespread requirements for SWI/SNF and RSC on transcription including strong evidence that SWI/SNF directly represses iron transport genes.