Project description:RELATIVE OF EARLY FLOWERING 6 (REF6/JMJ12), a Jumonji C (JmjC)-domain-containing histone demethylase, directly recognizes the CTCTGYTY motif by its zinc-finger domains to demethylate H3K27me3 at specific loci in Arabidopsis genome. Here we show that the recognition of CTCTGYTY motif by REF6 is prevented by DNA methylation. REF6 prefers to bind DNA hypo-methylated regions in vivo. DNA cytosine-methylation decreases REF6 binding affinity in vitro, and the crystal structure of ZnF-clusters showed that REF6 prefers unmethylated DNA sequences. Furthermore, REF6 displayed ectopic binding on multiple new target loci in drm1 drm2 cmt2 cmt3 (ddcc) quadruple mutants, where non-CG methylation was largely diminished. Collectively, this study reveals a novel targeting crosstalk between an H3K27me3 demethylase and DNA methylation.
Project description:We report genome-wide binding targets of REF6, a H3K27me3 demethylase and also high-throughput profiling of histone modifications of H3K27me3 in Arabidopsis flowers. Using chromatin-immunoprecipitation followed by high-throughput sequencing, we mapped thousands of binding targets of REF6 in flowers and in addition, we used a second fixative, DSG to capture more indirect targets of REF6. In order to investigate the function of indirect binding of REF6 represented H3K27me3 demethylase, the binding targets of DNA binding domain deleted REF6 were identified in the triple mutant background in which REF6 and its two homologs were mutated. Meanwhile, the H3K27me3 marked regions in both wild type and triple mutant flowers were defined. By analyzing the differentially enriched H3K27me3 region and REF6 binding profile, we found that REF6 functions to determine the boundary of H3K27me3 regions. Comparison of binding profiles of REF6 in flowers and in seedlings (ref) revealed a tissue-specific binding manner. More importantly, we found that the indirect binding of REF6 is mediated by trans factors and this indirect binding is crucial for REF6 function, especially in reproductive organs in Arabidopsis. Our results provide novel molecular insights into REF6 functions.
Project description:We report genome-wide binding targets of REF6, a H3K27me3 demethylase and also high-throughput profiling of histone modifications of H3K27me3 in Arabidopsis flowers. To further investigate the downstream targets of REF6 represented H3K27me3 demethylase, we performed RNA-seq using single, double mutant and triple mutant. Using chromatin-immunoprecipitation followed by high-throughput sequencing, we mapped thousands of binding targets of REF6 in flowers and in addition, we used a second fixative, DSG to capture more indirect targets of REF6. In order to investigate the function of indirect binding of REF6 represented H3K27me3 demethylase, the binding targets of DNA binding domain deleted REF6 were identified in the triple mutant background in which REF6 and its two homologs were mutated. Meanwhile, the H3K27me3 marked regions in both wild type and triple mutant flowers were defined. By analyzing the differentially enriched H3K27me3 region and REF6 binding profile, we found that REF6 functions to determine the boundary of H3K27me3 regions. Comparison of binding profiles of REF6 in flowers and in seedlings (ref) revealed a tissue-specific binding manner. More importantly, we found that the indirect binding of REF6 is mediated by trans factors and this indirect binding is crucial for REF6 function, especially in reproductive organs in Arabidopsis. Our results provide novel molecular insights into REF6 functions.
Project description:RELATIVE OF EARLY FLOWERING 6 (REF6, also known as JMJ12) counteracts Polycomb mediated gene silencing through demethylating histone H3 lysine 27 trimethylation (H3K27me3) in Arabidopsis. Genome-wide analysis has demonstrated that REF6 dependent H3K37me3 demethylation occurs on hundreds of genes. However, how these genes are selectively subjected to H3K27me3 demethylation remains elusive. Here we show that a tandem array of four Cys2-His2 zinc finger domains (C2H2-ZF) at REF6 C-terminus are essential for REF6 function. Mechanistically, we find that C2H2-ZF cluster can directly recognize a specific DNA sequence motif, and is essential for binding of REF6 to its targets. In addition, we demonstrate that CUP-SHAPED COTYLEDON 1 (CUC1) and CUC3 harbor such sequence motif and are direct targets of REF6; while their close homolog, CUC2, without such binding motif is not bound by REF6. Furthermore, REF6 is essential for proper H3K27me3 level at CUC1 locus, CUC1 activation and cotyledon separation. Collectively, our study reveals not only a novel mechanism of H3K27me3 demethylase genome targeting to counteract Polycomb silencing, but also a new function of H3K27me3 demethylation in organ boundary formation. All seeds, except for H3K9me2 ChIP-seq, were grown on 1/2MS plate at 23°C under long day condition. 12 day after germination (12DAG), whole seedling were harvested for ChIP-seq. anti-HA ChIP-seq were performed with three samples: Col (WT,Negtive control), REF6-HA(REF6p::REF6-HA ref6-1),REF6-ZnF-HA(REF6p::REF6-ZnF-HA ref6-1). anti-H3K27me3 ChIP-seq were performed with four samples: Col (WT), ref6-1 (mutant), REF6-HA(REF6p::REF6-HA ref6-1),REF6-ZnF-HA(REF6p::REF6-ZnF-HA ref6-1).For H3K9me2 ChIP-seq, plants were grown in soil at 23°C under long day condition. Aerial part of plants were harvested for ChIP-seq 28d after germination.
Project description:RELATIVE OF EARLY FLOWERING 6 (REF6, also known as JMJ12) counteracts Polycomb mediated gene silencing through demethylating histone H3 lysine 27 trimethylation (H3K27me3) in Arabidopsis. Genome-wide analysis has demonstrated that REF6 dependent H3K37me3 demethylation occurs on hundreds of genes. However, how these genes are selectively subjected to H3K27me3 demethylation remains elusive. Here we show that a tandem array of four Cys2-His2 zinc finger domains (C2H2-ZF) at REF6 C-terminus are essential for REF6 function. Mechanistically, we find that C2H2-ZF cluster can directly recognize a specific DNA sequence motif, and is essential for binding of REF6 to its targets. In addition, we demonstrate that CUP-SHAPED COTYLEDON 1 (CUC1) and CUC3 harbor such sequence motif and are direct targets of REF6; while their close homolog, CUC2, without such binding motif is not bound by REF6. Furthermore, REF6 is essential for proper H3K27me3 level at CUC1 locus, CUC1 activation and cotyledon separation. Collectively, our study reveals not only a novel mechanism of H3K27me3 demethylase genome targeting to counteract Polycomb silencing, but also a new function of H3K27me3 demethylation in organ boundary formation.
Project description:BRAHMA (BRM) is a conserved SWI/SNF-type chromatin remodeling ATPase implicated in many key nuclear events. Histone H3 Lysine 27 (H3K27) demethylases specifically remove the repressive histone mark, trimethylation of H3K27 (H3K27me3). Both proteins are thought to play active roles in regulating gene activities at the chromatin level, but their genome-wide coordination remains to be determined. In Arabidopsis thaliana, RELATIVE OF EARLY FLOWERING 6 (REF6, also known as JMJ12) is the first identified plant H3K27 demethylase. Here, genome-wide analyses revealed that REF6 targets to thousands of genes across the Arabidopsis genome and co-localizes with BRM at more than 1,000 genes, many of which are genes involved in response to various stimuli, especially plant hormones. Loss of REF6 activity results in decreased BRM occupancy at hundreds of BRM-REF6 co-targets, indicating that REF6 is required for the recruitment of BRM to chromatin. Further, REF6 targets to genomic loci that contains the CTCTGTTT motif in vivo
Project description:We report transcriptome changes and genome-wide dynamics of H3K27me3 during seed germination in Arabidopdsis, and investigate the impact of REF6-mediated H3K27 demethylation on germination. Compared with transcriptome changes, we discover delayed H3K27me3 reprogramming closely associated with the embryo to vegetative cell fate switch. REF6-mediated H3K27 demethylation promotes germination but does not significantly contribute to H3K27me3 dynamics during germination, but rather stably establishes an H3K27me3-depleted state permissive to transcription. By analyzing REF6 genomic binding, we show that it is absent from mature embryo chromatin and gradually establishes occupancy during the course of germination to counteract increased PRC2 activity.
Project description:Dynamic trimethylation of histone H3 at Lys27 (H3K27me3) affects gene expression and controls plant development and environmental responses. In Arabidopsis thaliana, RELATIVE OF EARLY FLOWERING 6/JUMONJI DOMAIN-CONTAINING PROTEIN 12 (REF6/JMJ12) demethylates H3K27me3 by recognizing a specific DNA motif; however, little is known about how REF6 activates target gene expression after recognition, especially in environmental responses. In response to warm ambient temperature, plants undergo thermomorphogenesis, which involves accelerated growth, early flowering, and changes in morphology. Here we show that REF6 regulates thermomorphogenesis and cooperates with the transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4) to synergistically activate thermo-responsive genes under warm ambient temperature. The ref6 loss-of-function mutants exhibited attenuated hypocotyl elongation at warm temperature, partially due to down-regulation of GIBBERELLIN 20-OXIDASE2 (GA20ox2) and BASIC HELIX-LOOP-HELIX 87 (bHLH87). REF6 enzymatic activity is necessary for warm ambient temperature responses. Together, our results provide direct evidence of an epigenetic modifier and a transcription factor working together to respond to the environment.
Project description:We demonstrate that REF6/JMJ12 (RELATIVE OF EARLY FLOWERING 6/Jumonji domain-containing protein 12) is an H3K27me3 and H3K27me2 demethylase. Plants overexpressing REF6/JMJ12 resemble mutants defective in H3K27me3-mediated gene silencing. Genetic interaction tests indicate that REF6/JMJ12 acts downstream of H3K27me3 methyltransferases. Moreover, loss of REF6/JMJ12 leads to ectopic and increased H3K27me3 and decreased mRNA expression of a large spectrum of genes involved in development and hormone responses to stimuli. Expression array to identify differentially expressed genes in ref6-1. For genome-wide expression analysis of ref6/jmj12, two replicates of Col and ref6/jmj12 samples (RNA from 10-day-old whole seedlings on MS plates in long day conditions at 23 degrees) were analyzed on an Affymetrix ATH1 chip by an Affymetrix service facility (CapitalBio Corporation) according to the manufacturer's protocols. Genes showing a 20.6-fold change with a q-value < 0.05 were considered as differentially expressed.
Project description:We demonstrate that REF6/JMJ12 (RELATIVE OF EARLY FLOWERING 6/Jumonji domain-containing protein 12) is an H3K27me3 and H3K27me2 demethylase. Plants overexpressing REF6/JMJ12 resemble mutants defective in H3K27me3-mediated gene silencing. Genetic interaction tests indicate that REF6/JMJ12 acts downstream of H3K27me3 methyltransferases. Moreover, loss of REF6/JMJ12 leads to ectopic and increased H3K27me3 and decreased mRNA expression of a large spectrum of genes involved in development and hormone responses to stimuli.