Bifunctional Activity of members of the Arabidopsis NF-YA Transcription Factor Family
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ABSTRACT: Five members of the Arabidopsis thaliana NF-YA gene family are strongly induced by several stress conditions via transcriptional and miR169-related posttranscriptional mechanisms. These transcription factors participate in gene regulation via two different mechanisms, one depending on binding to the CCAAT-box in the promoter of regulated genes and the other, independent of the CCAAT-box, in which NF-YA prevents the interaction of the NF-YB/YC heterodimer with transcription factors. Three biological and two technical (in swap) replicates for each genotype were obtained for each treatment (DMSO (mock) and estradiol 24h after induction). Mock samples were pooled and used as a reference.
Project description:Five members of the Arabidopsis thaliana NF-YA gene family are strongly induced by several stress conditions via transcriptional and miR169-related posttranscriptional mechanisms. These transcription factors participate in gene regulation via two different mechanisms, one depending on binding to the CCAAT-box in the promoter of regulated genes and the other, independent of the CCAAT-box, in which NF-YA prevents the interaction of the NF-YB/YC heterodimer with transcription factors.
Project description:Nuclear Factor Y (NF-Y) is a heterotrimeric transcription factor that binds CCAAT elements. The NF-Y trimer is composed of a Histone Fold Domain (HFD) dimer (NF-YB/NF-YC) and NF-YA, which confers DNA sequence specificity. NF-YA shares a conserved domain with the CONSTANS, CONSTANS-LIKE, TOC1 (CCT) proteins. We show that CONSTANS (CO/B-BOX PROTEIN1 BBX1), a master flowering regulator, forms a trimer with Arabidopsis thaliana NF-YB2/NF-YC3 to efficiently bind the CORE element of the FLOWERING LOCUS T promoter. Using saturation mutagenesis, electrophoretic mobility shift assays, and RNA-sequencing profiling of co, nf-yb, and nf-yc mutants, we identify CCACA elements as the core NF-CO binding site. CO physically interacts with the same HFD surface required for NF-YA association, as determined by mutations in NF-YB2 and NF-YC9, and tested in vitro and in vivo. The co-7 mutation in the CCT domain, corresponding to an NF-YA arginine directly involved in CCAAT recognition, abolishes NF-CO binding to DNA
Project description:Cell type-specific master transcription factors (MTFs) play vital roles in defining cell identity and function. However, the roles ubiquitous factors play in the specification of cell identity remain underappreciated. Here we show that all three subunits of the ubiquitous heterotrimeric CCAAT-binding NF-Y complex are required for the maintenance of embryonic stem cell (ESC) identity, and establish NF-Y as a novel component of the core pluripotency network. Genome-wide occupancy and transcriptomic analyses in ESCs and neurons reveal that not only does NF-Y regulate genes with housekeeping functions through cell type-invariant promoter-proximal binding, but also genes required for cell identity by binding to cell type-specific enhancers with MTFs. Mechanistically, NF-Y's distinctive DNA-binding mode promotes MTF binding at enhancers by facilitating a permissive chromatin conformation. Our studies unearth a novel function for NF-Y in promoting chromatin accessibility, and suggest that other proteins with analogous structural and DNA-binding properties may function in similar ways. Genome-wide mapping of NF-YA, NF-YB, and NF-YC subunits of the NF-Y complex in mouse ESCs, and microarray gene expression profiling of control knockdown (KD), NF-YA KD, NF-YB KD, NF-YC KD, and NF-YA/NF-YB/NF-YC triple KD ESCs.
Project description:The trimeric transcription factor -TF- NF-Y binds to the CCAAT box, an element enriched in promoters of genes overexpressed in tumors. The NF-YC subunit was recently identified as an oncogene in choroid plexus carcinomas. Previous studies on the NF-Y regulome identified the general term metabolism as significantly enriched. We dissect here in detail the targeting of metabolic genes by integrating analysis of NF-Y genomic binding and profilings after inactivation of NF-Y subunits in different cell types. NF-Y comprehensively controls de novo biosynthetic pathways of lipids, teaming up with the master SREBPs regulators. It activates glycolytic genes, but, surprisingly, is neutral, or represses mitochondrial respiratory genes. NF-Y targets the SOCG (Serine, One Carbon, Glycine) and Glutamine pathways, as well as genes involved in the biosynthesis of polyamines and purines. Within the different pathways, cancer-driving nodes are under NF-Y positive control. Altogether, these data delineate a coherent strategy to promote expression of metabolic genes fuelling anaerobic energy production, and other anabolic pathways commonly altered in cancer cells. Scrambled control (shSCM) and NF-YA pLKO.1-shRNAs were designed by Sigma-Aldrich. The puromycin resistance cassette was replaced with an EGFP cassette. Viral production and transduction were carried out as previously described (Benatti et al. 2011). H322 and HCT116 were transduced with shSC or shNF-YA viral supernatants, in triplicates and cells collected after 72 hours. RNA was prepared according to Affymetrix standard protocol and hybridized to Hu-Gene 2.0 expression arrays. H322 and HCT116 were transduced with shSC and shNF-YA and harvest after 72 hours
Project description:NF-Y, a trimeric transcription factor (TF) composed of two histone-like subunits (NF-YB (NFYB) and NF-YC (NFYC)) and a sequence-specific subunit (NF-YA), binds to the CCAAT motif, a common promoter element. Genome-wide mapping reveals 5,000-15,000 NF-Y binding sites depending on the cell type, with the NF-YA and NF-YB subunits binding asymmetrically with respect to the CCAAT motif. Despite being characterized as a proximal promoter TF, only 25% of NF-Y sites map to promoters. A comparable number of NF-Y sites are located at enhancers, many of which are tissue specific, and nearly half of NF-Y sites are in select subclasses of HERV LTR repeats. Unlike most TFs, NF-Y can access its target DNA motif in inactive (non-modified) or polycomb-repressed chromatin domains. Unexpectedly, NF-Y extensively co-localizes with FOS in all genomic contexts, and at promoters and enhancers this often occurs in the absence of JUN and the AP-1 motif. NF-Y also co-associates with a select cluster of growth-controlling and oncogenic TFs, consistent with the abundance of CCAAT motifs in the promoters of genes overexpressed in cancer. Interestingly, NF-Y and several growth-controlling TFs bind in a stereo-specific manner, suggesting a mechanism for cooperative action at promoters and enhancers. Our results indicate that NF-Y is not merely a commonly-used, proximal promoter TF, but rather performs a more diverse set of biological functions, many of which are likely to involve co-association with FOS. Scrambled control (shSCM) and NF-YA pLKO.1-shRNAs were designed by Sigma-Aldrich. The puromycin resistance cassette was replaced with an EGFP cassette. Viral production and transduction were carried out as previously described (Benatti et al. 2011). HeLaS3 cells were transduced with shSCM or shNF-YA viral supernatants, in triplicate, and cells collected after 48 hr of incubation. Total RNA was prepared by Trizol extraction and Qiagen RNeasy kit purification, converted to biotinylated aRNA and hybridized to U133 Plus 2.0 GeneChip expression arrays using the 3’ IVT Express Kit (Affymetrix, USA) following the manufacturer’s protocol. Arrays were RMA normalized (Irizarry et al. 2003), gene expression levels calculated, differential expression determined using the following R packages from the Bioconductor project: affy (Gautier et al. 2004), limma (Smyth 2004). HelaS3 cells were transduced with shSCM or shNF-YA in triplicate for 48hrs.
Project description:NF-Y is a trimeric transcription factor whose binding site -the CCAAT box- is enriched in cancer-promoting genes. The regulatory subunit, the sequence-specificity conferring NF-YA, comes in two major isoforms, NF-YA long (NF-YAl) and short (NF-YAs). Extensive expression analysis in epithelial cancers determined two features: widespread overexpression and changes in NF-YAl/NF-Ys ratios (NF-YAr) in tumors with EMT features. We performed wet and in silico experiments to explore the role of the NF-YA isoforms in breast -BRCA- and gastric -STAD- cancers. We generated clones of two Claudinlow BRCA lines BT549 and SUM159PT ablated of exon-3, thus shifting expression from NF-YAl to NF-YAs. Edited clones show normal growth, but reduced migratory capacities in vitro, and ability to metastatize in vivo. Using TCGA, including upon deconvolution of scRNA-seq data, we formalize the clinical importance of high NF-YAr, associated to EMT genes and cell populations. We derive a novel, 158 genes signature common to BRCA and STAD Claudinlow tumors. Finally, we identify splicing factors associated to high NF-YAr, further validating RBFOX2 as promoting expression of NF-YAl with wet experiments. In conclusion, these data bring three relevant results: (i) concerning Claudinlow tumors, the definition and clinical implications of NF-YAr and the 158 genes signature; (ii) genetic evidence of a role of exon-3 28 aminoacids, empowering NF-YAl with EMT-driving features in BRCA. (iii) The definition of a set of splicing factors fine-tuning the levels of NF-YA isoforms.
Project description:Cell type-specific master transcription factors (MTFs) play vital roles in defining cell identity and function. However, the roles ubiquitous factors play in the specification of cell identity remain underappreciated. Here we show that all three subunits of the ubiquitous heterotrimeric CCAAT-binding NF-Y complex are required for the maintenance of embryonic stem cell (ESC) identity, and establish NF-Y as a novel component of the core pluripotency network. Genome-wide occupancy and transcriptomic analyses in ESCs and neurons reveal that not only does NF-Y regulate genes with housekeeping functions through cell type-invariant promoter-proximal binding, but also genes required for cell identity by binding to cell type-specific enhancers with MTFs. Mechanistically, NF-Y's distinctive DNA-binding mode promotes MTF binding at enhancers by facilitating a permissive chromatin conformation. Our studies unearth a novel function for NF-Y in promoting chromatin accessibility, and suggest that other proteins with analogous structural and DNA-binding properties may function in similar ways. Genome-wide mapping of NF-YA, NF-YB, and NF-YC subunits of the NF-Y complex in mouse ESCs, and microarray gene expression profiling of control knockdown (KD), NF-YA KD, NF-YB KD, NF-YC KD, and NF-YA/NF-YB/NF-YC triple KD ESCs.
Project description:NF-Y, a trimeric transcription factor (TF) composed of two histone-like subunits (NF-YB (NFYB) and NF-YC (NFYC)) and a sequence-specific subunit (NF-YA), binds to the CCAAT motif, a common promoter element. Genome-wide mapping reveals 5,000-15,000 NF-Y binding sites depending on the cell type, with the NF-YA and NF-YB subunits binding asymmetrically with respect to the CCAAT motif. Despite being characterized as a proximal promoter TF, only 25% of NF-Y sites map to promoters. A comparable number of NF-Y sites are located at enhancers, many of which are tissue specific, and nearly half of NF-Y sites are in select subclasses of HERV LTR repeats. Unlike most TFs, NF-Y can access its target DNA motif in inactive (non-modified) or polycomb-repressed chromatin domains. Unexpectedly, NF-Y extensively co-localizes with FOS in all genomic contexts, and at promoters and enhancers this often occurs in the absence of JUN and the AP-1 motif. NF-Y also co-associates with a select cluster of growth-controlling and oncogenic TFs, consistent with the abundance of CCAAT motifs in the promoters of genes overexpressed in cancer. Interestingly, NF-Y and several growth-controlling TFs bind in a stereo-specific manner, suggesting a mechanism for cooperative action at promoters and enhancers. Our results indicate that NF-Y is not merely a commonly-used, proximal promoter TF, but rather performs a more diverse set of biological functions, many of which are likely to involve co-association with FOS. Scrambled control (shSCM) and NF-YA pLKO.1-shRNAs were designed by Sigma-Aldrich. The puromycin resistance cassette was replaced with an EGFP cassette. Viral production and transduction were carried out as previously described (Benatti et al. 2011). HeLaS3 cells were transduced with shSCM or shNF-YA viral supernatants, in triplicate, and cells collected after 48 hr of incubation. Total RNA was prepared by Trizol extraction and Qiagen RNeasy kit purification, converted to biotinylated aRNA and hybridized to U133 Plus 2.0 GeneChip expression arrays using the 3’ IVT Express Kit (Affymetrix, USA) following the manufacturer’s protocol. Arrays were RMA normalized (Irizarry et al. 2003), gene expression levels calculated, differential expression determined using the following R packages from the Bioconductor project: affy (Gautier et al. 2004), limma (Smyth 2004).
Project description:The trimeric transcription factor -TF- NF-Y binds to the CCAAT box, an element enriched in promoters of genes overexpressed in tumors. The NF-YC subunit was recently identified as an oncogene in choroid plexus carcinomas. Previous studies on the NF-Y regulome identified the general term metabolism as significantly enriched. We dissect here in detail the targeting of metabolic genes by integrating analysis of NF-Y genomic binding and profilings after inactivation of NF-Y subunits in different cell types. NF-Y comprehensively controls de novo biosynthetic pathways of lipids, teaming up with the master SREBPs regulators. It activates glycolytic genes, but, surprisingly, is neutral, or represses mitochondrial respiratory genes. NF-Y targets the SOCG (Serine, One Carbon, Glycine) and Glutamine pathways, as well as genes involved in the biosynthesis of polyamines and purines. Within the different pathways, cancer-driving nodes are under NF-Y positive control. Altogether, these data delineate a coherent strategy to promote expression of metabolic genes fuelling anaerobic energy production, and other anabolic pathways commonly altered in cancer cells. Scrambled control (shSCM) and NF-YA pLKO.1-shRNAs were designed by Sigma-Aldrich. The puromycin resistance cassette was replaced with an EGFP cassette. Viral production and transduction were carried out as previously described (Benatti et al. 2011). H322 and HCT116 were transduced with shSC or shNF-YA viral supernatants, in triplicates and cells collected after 72 hours. RNA was prepared according to Affymetrix standard protocol and hybridized to Hu-Gene 2.0 expression arrays.