Project description:The nuclear matrix was identified as a nuclear fraction in eukaryotic cells that offers a supporting scaffold for chromatin. While the structure is known in plant nuclei for decades, the distribution of regions attaching at plant nuclei, and how the nuclear matrix influences chromatin status is largely unkown. Here, we identify novel proteins, FRS7 (FAR1 RELATED SEQUENCE 7) and FRS12, attaching chromatin regions at the nuclear matrix in Arabidopsis thaliana. We found the above two proteins cooperate with AHL22 (AT-hook Motif Nuclear Localized 22) in repress hypocotyl elongation, by recruiting chromatin regions and histone deacetylases to the nuclear matrix and silence the genes. These findings shed light on understanding regulation and roles of the nuclear matrix influence in epigenetic and transcriptional regulation in Arabidopsis.
Project description:Polypyrimidine tract-binding protein homologues from Arabidopsis are key regulators of alternative splicing with implications in fundamental developmental processes
Project description:JASMONATE-ZIM DOMAIN (JAZ) proteins are key regulators in the JA signaling pathway and function to repress the expression of JA-responsive genes. We found that JAZ proteins directly interact with several chromatin-associated Polycomb proteins to mediate repressive chromatin modifications at part of JA-responsive genes and thus their transcriptional repression in Arabidopsis.
Project description:We developed a stringent selection pipeline for lncRNA identification, combining high-throughput RNA sequencing and computational approaches. Using this pipeline, we annotated 1,353 lncRNAs in Arabidopsis thaliana. We further found that one fifth of the lncRNAs were associated with Polycomb repressive complex 2 (PRC2). Some PRC2-associated lncRNAs could repress the transcription of their neighboring genes through mediating histone H3 lysine 27 trimethylation.
Project description:The Polycomb Group (PcG) proteins form two protein complexes, PcG Repressive Complex 1 (PRC1) and PRC2, which are key epigenetic regulators in eukaryotes. PRC2 represses gene expression by catalyzing the trimethylation of histone H3 lysine 27 (H3K27me3). In Arabidopsis (Arabidopsis thaliana), CURLY LEAF (CLF) and SWINGER (SWN) are two major H3K27 methyltransferases and core components of PRC2, playing essential roles in plant growth and development. Despite their importance, genome-wide binding profiles of CLF and SWN have not been determined and compared yet. In this study, we generated transgenic lines expressing GFP-tagged CLF/SWN under their respective native promoters and used them for ChIP-seq analyses to profile the genome-wide distributions of CLF and SWN in Arabidopsis seedlings. We also profiled and compared the global H3K27me3 levels in wild-type (WT) and PcG mutants (clf, swn, and clf swn). Our data show that CLF and SWN bind to almost the same set of genes, except that SWN has a few hundred more targets. Two short DNA sequences, the GAGA-like and Telo-box-like motifs, were found enriched in the CLF and SWN binding regions. The H3K27me3 levels in clf, but not in swn, were markedly reduced compared with WT; and the mark was undetectable in the clf swn double mutant. Further, we profiled the transcriptomes in clf, swn, and clf swn, and compared with that in WT. Thus this work provides a useful resource for the plant epigenetics community for dissecting the functions of PRC2 in plant growth and development.
Project description:Histone marks H3K27me3 and H3K4me3 are mutual exclusive over plant genome, however, the underlying mechanism is not fully understood. Arabidopsis telomeric repeat binding factors (TRBs) are required for the deposition of H3K27me3 by recruiting Polycomb repressive complexes (PRCs). Here, we demonstrate that TRBs associate and colocalize with JUMONJI 14 (JMJ14) over gene body regions and trigger H3K4me3 demethylation. The trb1/2/3 triple mutant and jmj14-1 mutant show an increased level of H3K4me3 over TRB and JMJ14 binding sites, resulting in up-regulation of their targeting genes. Furthermore, tethering TRBs to the promoter region of genes with an artificial zinc finger successfully triggers target gene silencing. These results suggest that TRB proteins cooperate with PRC2 and JMJ14 complex to repress target gene by H3K4me3 demethylation and H3K27me3 deposition.
Project description:DELLA proteins act as hubs that relay environmental information to the multiple transcriptional circuits that control growth and development through physical interaction with transcription factors from different families. We have analyzed the presence of one DELLA protein at the Arabidopsis genome by chromatin immunoprecipitation coupled to large-scale sequencing and we find that it binds at the promoters of multiple genes. Enrichment analysis shows a strong preference for cis elements recognized by specific transcription factor families. In particular, we demonstrate that DELLA proteins are recruited by type-B ARABIDOPSIS RESPONSE REGULATORS (ARR) to the promoters of cytokinin-regulated genes, where they act as transcriptional co-activators. The biological relevance of this mechanism is underpinned by the necessity of simultaneous presence of DELLAs and ARRs to restrict root meristem growth and to promote photomorphogenesis.
Project description:Polycomb group (PcG) proteins are highly conserved from flies to mammals and many of these factors have essential roles in early embryonic development. PcG proteins comprise two multimeric complexes, the Polycomb Repressive complexes 1 and 2 (PRC1 and 2), which have been shown to repress transcription through epigenetic modification of chromatin structure. To gain insight into the role of Polycomb in early development, we have identified PRC1 and PRC2 target genes in mouse embryonic stem (ES) cells using genome-scale location analysis. We found that PRC2 occupies many genes that encode key regulators of development including those encoding transcription factors and components of signaling pathways. These genes are repressed and contain nucleosomes methylated at lysine 27 on histone H3. The majority of PRC2 bound and methylated target genes are co-occupied by PRC1 indicating that these complexes function at a similar set of genes in ES cells. Lack of PRC1 or PRC2 subunits in ES cells results in derepression of target genes and loss of pluripotency. These results provide insight into how PcG proteins contribute to the maintenance of stem cell identity.