Project description:Plant BBR/BPC transcription factors contain the conserved Basic-Pentacystein (BPC) DNA-binding domain. Arabidopsis group II BBR/BPC proteins interact with PRC1 component LHP1 in vivo. Microarray experiments with Arabidopsis bpc4 bpc6, lhp1-4 and lhp1-4 bpc4 bpc6 suggest an importance of this interaction in the concerted repression of homeotic genes. In this study, we used the ATH1 GeneChip microarray to investigate transcript abundance in different Arabidopsis thaliana genotypes.
Project description:Plant BBR/BPC transcription factors contain the conserved Basic-Pentacystein (BPC) DNA-binding domain. Arabidopsis group II BBR/BPC proteins interact with PRC1 component LHP1 in vivo. Microarray experiments with Arabidopsis bpc4 bpc6, lhp1-4 and lhp1-4 bpc4 bpc6 suggest an importance of this interaction in the concerted repression of homeotic genes. In this study, we used the ATH1 GeneChip microarray to investigate transcript abundance in different Arabidopsis thaliana genotypes. Arabidopsis thaliana (accession Columbia) were grown in the greenhouse under constant temperature of 20°C, 35% humidity and a 18-h light period. 18 days old plants were harvested and immediately frozen in liquid nitrogen. Six individual plants were pooled per replicate.
Project description:PcG regulation in Arabidopsis is required to maintain cell differentiation and to allow developmental phase transitions. This is achieved by the activity of three PRC2s and the participation of a yet poorly defined PRC1. Previous results showed that apparent PRC1 components perform discrete roles during plant development, suggesting the existence of PRC1 variants; however, it is not clear in how many processes these components participate. We show that AtBMI1 proteins are required to promote all developmental phase transitions and to control cell proliferation during organ growth and development, expanding their proposed range of action. While AtBMI1 function during germination is closely linked to B3 domain transcription factors VAL1/2 possibly in combination with GT-box binding factors, other AtBMI1 regulatory networks require participation of different factor combinations. Conversely, EMF1 and LHP1 bind many H3K27me3 positive genes upregulated in atbmi1a/b/c mutants; however, loss of their function affects expression of a different subset, suggesting that even if EMF1, LHP1 and AtBMI1 exist in a common PRC1 variant, their role in repression depends on the functional context.
Project description:By RNA deep sequencing, around 11,000 genes were found to be differentially expressed in ebs shl lhp1 compared with wild type, and SHL and EBS, together with LHP1 and EMF1, co-regulate the expression of thousands of gene in Arabidopsis
Project description:BACKGROUND: Polycomb group complexes PRC1 and PRC2 repress gene expression at the chromatin level in eukaryotes. The classic recruitment model of Polycomb group complexes in which PRC2-mediated H3K27 trimethylation recruits PRC1 for H2A monoubiquitination was recently challenged by data showing that PRC1 activity can also recruit PRC2. However, the prevalence of these two mechanisms is unknown, especially in plants as H2AK121ub marks were examined at only a handful of Polycomb group targets. RESULTS: By using genome-wide analyses, we show that H2AK121ub marks are surprisingly widespread in Arabidopsis thaliana, often co-localizing with H3K27me3 but also occupying a set of transcriptionally active genes devoid of H3K27me3. Furthermore, by profiling H2AK121ub and H3K27me3 marks in atbmi1a/b/c, clf/swn, and lhp1 mutants we found that PRC2 activity is not required for H2AK121ub marking at most genes. In contrast, loss of AtBMI1 function impacts the incorporation of H3K27me3 marks at most Polycomb group targets. CONCLUSIONS: Our findings show the relationship between H2AK121ub and H3K27me3 marks across the A. thaliana genome and unveil that ubiquitination by PRC1 is largely independent of PRC2 activity in plants, while the inverse is true for H3K27 trimethylation.
Project description:BACKGROUND: Polycomb group complexes PRC1 and PRC2 repress gene expression at the chromatin level in eukaryotes. The classic recruitment model of Polycomb group complexes in which PRC2-mediated H3K27 trimethylation recruits PRC1 for H2A monoubiquitination was recently challenged by data showing that PRC1 activity can also recruit PRC2. However, the prevalence of these two mechanisms is unknown, especially in plants as H2AK121ub marks were examined at only a handful of Polycomb group targets. RESULTS: By using genome-wide analyses, we show that H2AK121ub marks are surprisingly widespread in Arabidopsis thaliana, often co-localizing with H3K27me3 but also occupying a set of transcriptionally active genes devoid of H3K27me3. Furthermore, by profiling H2AK121ub and H3K27me3 marks in atbmi1a/b/c, clf/swn, and lhp1 mutants we found that PRC2 activity is not required for H2AK121ub marking at most genes. In contrast, loss of AtBMI1 function impacts the incorporation of H3K27me3 marks at most Polycomb group targets. CONCLUSIONS: Our findings show the relationship between H2AK121ub and H3K27me3 marks across the A. thaliana genome and unveil that ubiquitination by PRC1 is largely independent of PRC2 activity in plants, while the inverse is true for H3K27 trimethylation.
Project description:ASYMMETRIC LEAVES 1 (AS1) is an important transcription factor for leaf development in Arabidopsis. But how it regulates downstream genes is largely unknown. We found a co-factor of AS1, LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), also named as TERMINAL FLOWER 2 (TFL2), a PcG protein in Arabidopsis. To further investigate how AS1 and LHP1 co-regulate downstream genes at the genome level, we perform the transcriptome analysis of as1-1, tfl2-1, and as1-1 tfl2-1 in comparison with wild type (WT).
Project description:Polycomb repressive complexes (PRCs) play key roles in developmental epigenetic regulation. Yet the mechanisms that target PRCs to specific loci in mammalian cells remain incompletely understood. In this study, we show that Bmi1, a core component of Polycomb Repressive Complex 1 (PRC1), binds directly to the Runx1/CBFbeta transcription factor complex. Genome-wide studies in megakaryocytic cells demonstrate considerable chromatin occupancy overlap between the PRC1 core component Ring1b and Runx1/CBFbeta and functional regulation of a significant fraction of commonly bound genes. Bmi1/Ring1b and Runx1/CBFbeta deficiency generate partial phenocopies of one another in vivo. We also show that Ring1b occupies key Runx1 binding sites in primary murine thymocytes and that this occurs via Polycomb Repressive Complex 2 (PRC2) independent mechanisms. Genetic depletion of Runx1 results in reduced Ring1b binding at these sites in vivo. These findings provide evidence for site-specific PRC1 chromatin recruitment by core binding transcription factors in mammalian cells. shRNA mediated knockdown of CBFb, Ring1b and control in biological triplicate