scholarly journals Cold-induced Arabidopsis FRIGIDA nuclear condensates for FLC repression

Nature ◽  
2021 ◽  
Author(s):  
Pan Zhu ◽  
Clare Lister ◽  
Caroline Dean
Keyword(s):  
Antisense Rna ◽  
Transcriptional Repression ◽  
Seasonal Temperature ◽  
Warm Temperature ◽  
Polycomb Repressive Complex 2 ◽  
Dynamic Partitioning ◽  
Temperature Regimes ◽  
Floral Repressor ◽  
Natural Temperature ◽  
Local Levels

AbstractPlants use seasonal temperature cues to time the transition to reproduction. In Arabidopsis thaliana, winter cold epigenetically silences the floral repressor locus FLOWERING LOCUS C (FLC) through POLYCOMB REPRESSIVE COMPLEX 2 (PRC2)1. This vernalization process aligns flowering with spring. A prerequisite for silencing is transcriptional downregulation of FLC, but how this occurs in the fluctuating temperature regimes of autumn is unknown2–4. Transcriptional repression correlates with decreased local levels of histone H3 trimethylation at K36 (H3K36me3) and H3 trimethylation at K4 (H3K4me3)5,6, which are deposited during FRIGIDA (FRI)-dependent activation of FLC7–10. Here we show that cold rapidly promotes the formation of FRI nuclear condensates that do not colocalize with an active FLC locus. This correlates with reduced FRI occupancy at the FLC promoter and FLC repression. Warm temperature spikes reverse this process, buffering FLC shutdown to prevent premature flowering. The accumulation of condensates in the cold is affected by specific co-transcriptional regulators and cold induction of a specific isoform of the antisense RNA COOLAIR5,11. Our work describes the dynamic partitioning of a transcriptional activator conferring plasticity in response to natural temperature fluctuations, thus enabling plants to effectively monitor seasonal progression.

scholarly journals Identification of a PRC2 Accessory Subunit Required for Subtelomeric H3K27 Methylation in Neurospora crassa

2020 ◽  
Vol 40 (11) ◽  
Author(s):  
Kevin J. McNaught ◽  
Elizabeth T. Wiles ◽  
Eric U. Selker
Keyword(s):  
Neurospora Crassa ◽  
Transcriptional Repression ◽  
Sequence Similarity ◽  
Model Organism ◽  
Content Type ◽  
Polycomb Repressive Complex 2 ◽  
H3k27 Methylation ◽  
Accessory Subunit ◽  
Genomic Regions ◽  
Similarity Searches

ABSTRACT Polycomb repressive complex 2 (PRC2) catalyzes methylation of histone H3 at lysine 27 (H3K27) in genomic regions of most eukaryotes and is critical for maintenance of the associated transcriptional repression. However, the mechanisms that shape the distribution of H3K27 methylation, such as recruitment of PRC2 to chromatin and/or stimulation of PRC2 activity, are unclear. Here, using a forward genetic approach in the model organism Neurospora crassa, we identified two alleles of a gene, NCU04278, encoding an unknown PRC2 accessory subunit (PAS). Loss of PAS resulted in losses of H3K27 methylation concentrated near the chromosome ends and derepression of a subset of associated subtelomeric genes. Immunoprecipitation followed by mass spectrometry confirmed reciprocal interactions between PAS and known PRC2 subunits, and sequence similarity searches demonstrated that PAS is not unique to N. crassa. PAS homologs likely influence the distribution of H3K27 methylation and underlying gene repression in a variety of fungal lineages.

scholarly journals FBXO11-Mediated Proteolysis of BAHD1 Relieves PRC2-dependent Transcriptional Repression in Erythropoiesis

Blood ◽  
2020 ◽  
Author(s):  
Peng Xu ◽  
Daniel C. Scott ◽  
Beisi Xu ◽  
Yu Yao ◽  
Ruopeng Feng ◽  
...  
Keyword(s):  
Gene Expression ◽  
Ubiquitin Ligase ◽  
Transcriptional Repression ◽  
E3 Ubiquitin Ligase ◽  
Histone Mark ◽  
Developmentally Delayed ◽  
Hematopoietic Development ◽  
Polycomb Repressive Complex 2 ◽  
Stem And Progenitor Cells ◽  
Erythroid Maturation

The histone mark H3K27me3 and its reader/writer Polycomb repressive complex 2 (PRC2) mediate widespread transcriptional repression in stem and progenitor cells. Mechanisms that regulate this activity are critical for hematopoietic development but poorly understood. Here we show that the E3 ubiquitin ligase FBXO11 relieves PRC2-mediated repression during erythroid maturation by targeting its newly identified substrate BAHD1, an H3K27me3 reader that recruits transcriptional co-repressors. Erythroblasts lacking FBXO11 are developmentally delayed, with reduced expression of maturation-associated genes, most of which harbor bivalent histone marks (activating H3K4me3 and repressive H3K27me3), bind BAHD1, and fail to recruit the erythroid transcription factor GATA1. The BAHD1 complex interacts physically with PRC2 and depletion of either component restores FBXO11-deficient erythroid gene expression. Our studies identify BAHD1 as a novel effector of PRC2-mediated repression and reveal how a single E3 ubiquitin ligase eliminates PRC2 repression at developmentally poised bivalent genes during erythropoiesis.

scholarly journals Regulation of an antisense RNA with the transition of neonatal to IIb myosin heavy chain during postnatal development and hypothyroidism in rat skeletal muscle

2012 ◽  
Vol 302 (7) ◽  
pp. R854-R867 ◽  
Author(s):  
Clay E. Pandorf ◽  
Weihua Jiang ◽  
Anqi X. Qin ◽  
Paul W. Bodell ◽  
Kenneth M. Baldwin ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Myosin Heavy Chain ◽  
Postnatal Development ◽  
Heavy Chain ◽  
Antisense Rna ◽  
Transcriptional Repression ◽  
Mhc Genes ◽  
Regulatory Model ◽  
A Site ◽  
Comparative Phylogenetic Analysis

Postnatal development of fast skeletal muscle is characterized by a transition in expression of myosin heavy chain (MHC) isoforms, from primarily neonatal MHC at birth to primarily IIb MHC in adults, in a tightly coordinated manner. These isoforms are encoded by distinct genes, which are separated by ∼17 kb on rat chromosome 10. The neonatal-to-IIb MHC transition is inhibited by a hypothyroid state. We examined RNA products [mRNA, pre-mRNA, and natural antisense transcript (NAT)] of developmental and adult-expressed MHC genes (embryonic, neonatal, I, IIa, IIx, and IIb) at 2, 10, 20, and 40 days after birth in normal and thyroid-deficient rat neonates treated with propylthiouracil. We found that a long noncoding antisense-oriented RNA transcript, termed bII NAT, is transcribed from a site within the IIb-Neo intergenic region and across most of the IIb MHC gene. NATs have previously been shown to mediate transcriptional repression of sense-oriented counterparts. The bII NAT is transcriptionally regulated during postnatal development and in response to hypothyroidism. Evidence for a regulatory mechanism is suggested by an inverse relationship between IIb MHC and bII NAT in normal and hypothyroid-treated muscle. Neonatal MHC transcription is coordinately expressed with bII NAT. A comparative phylogenetic analysis also suggests that bII NAT-mediated regulation has been a conserved trait of placental mammals for most of the eutherian evolutionary history. The evidence in support of the regulatory model implicates long noncoding antisense RNA as a mechanism to coordinate the transition between neonatal and IIb MHC during postnatal development.

Contrasting Responses of Morphologically Similar Wheat Cultivars to Temperatures Appropriate to Warm Temperature Climates With Hot Summers: a Study in Controlled Environment

1977 ◽  
Vol 4 (6) ◽  
pp. 877 ◽  
Author(s):  
AK Bagga ◽  
HM Rawson
Keyword(s):  
Temperature Stability ◽  
Kernel Weight ◽  
Controlled Environment ◽  
Wheat Cultivars ◽  
Warm Temperature ◽  
Temperature Regimes ◽  
Wide Range ◽  
Phase Temperature ◽  
Warm Temperate ◽  
Plant Basis

This study attempted to determine if and why there are differences among three cultivars of wheat in their responses to temperature. The three semidwarf cultivars examined, Kalyansona, Condor and Janak, are currently used commercially. Temperature regimes chosen matched the range to which plants in warm temperate climates with hot summers would be exposed at different stages of development. Plants were grown in a phytotron in sunlit cabinets. Responses to temperature were different among the cultivars. Kalyansona was relatively un- responsive to temperatures during the floret phase, being little affected in the sizes of upper leaves, in floret production and grain set, in overall plant growth or in grain yield. The sole character to respond to temperature in this cultivar was kernel weight, which declined with increasing grain phase temperature. In contrast, Condor demonstrated marked plasticity during the floret phase in all plant characters measured. Its plasticity was such that, at the lower temperatures, it outyielded Kalyansona by a substantial margin while at the higher temperatures its yield was relatively poor. On a plant basis, Janak performed similarly to Condor. Rates of photosynthesis were relatively unaffected by temperature in any cultivar. This wide range of response among three superficially similar cultivars has promising implications for the tailoring of cultivars for different temperature zones. The importance of different plant characters to temperature stability is considered in the discussion.

scholarly journals Post-translational modifications of PRC2: signals directing its activity

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Yiqi Yang ◽  
Gang Li
Keyword(s):  
Catalytic Activity ◽  
Transcriptional Repression ◽  
Essential Role ◽  
Histone H3 ◽  
Post Translational Modifications ◽  
Polycomb Repressive Complex 2 ◽  
Cellular Identity ◽  
Organismal Development ◽  
Biochemical Signals ◽  
Insight Into

Abstract Polycomb repressive complex 2 (PRC2) is a chromatin-modifying enzyme that catalyses the methylation of histone H3 at lysine 27 (H3K27me1/2/3). This complex maintains gene transcriptional repression and plays an essential role in the maintenance of cellular identity as well as normal organismal development. The activity of PRC2, including its genomic targeting and catalytic activity, is controlled by various signals. Recent studies have revealed that these signals involve cis chromatin features, PRC2 facultative subunits and post-translational modifications (PTMs) of PRC2 subunits. Overall, these findings have provided insight into the biochemical signals directing PRC2 function, although many mysteries remain.

scholarly journals Natural variation in autumn FLC levels, rather than epigenetic silencing, aligns vernalization to different climates

2020 ◽  
Author(s):  
Jo Hepworth ◽  
Rea L Antoniou-Kourounioti ◽  
Kristina Berggren ◽  
Catja Selga ◽  
Eleri Tudor ◽  
...  
Keyword(s):  
Climatic Conditions ◽  
Epigenetic Silencing ◽  
Vernalization Response ◽  
Temperature Dependent ◽  
Climatic Fluctuations ◽  
Natural Variants ◽  
Floral Repressor ◽  
Natural Temperature ◽  
Long Timescales ◽  
Different Climates

AbstractPlants monitor temperatures over long timescales to assess seasons and time developmental transitions. In Arabidopsis thaliana, winter is registered during vernalization through the temperature-dependent repression and epigenetic silencing of floral repressor FLOWERING LOCUS C (FLC). Natural Arabidopsis accessions show considerable variation in vernalization, however which aspect of the FLC repression mechanism is most important for adaptation to different climates is not clear. By analyzing FLC silencing in natural variants throughout winter in three field sites, we find that FLC starting levels and early phases of silencing are the major variables underlying vernalization response, rather than establishment of epigenetic silencing. This results in an intricate interplay between promotion and delay of flowering to balance survival, and through a post-vernalization effect of FLC, reproductive effort via branch production. These data reveal how non-coding FLC variation aligns vernalization response to different climatic conditions and year-on-year fluctuations in natural temperature profiles.Impact StatementAlleles of the major floral repressor vary in their initial expression to underpin the ability of Arabidopsis to survive year-on-year climatic fluctuations.

scholarly journals Thermal sensitivity and seasonal change in the gut microbiome of a desert ant, Cephalotes rohweri

2021 ◽  
Author(s):  
Marshall S McMunn ◽  
Asher I Hudson ◽  
Ash Zemenick ◽  
Monika Egerer ◽  
Stacy M Philpott ◽  
...  
Keyword(s):  
Climate Change ◽  
Elevated Temperatures ◽  
Variable Temperature ◽  
Thermal Sensitivity ◽  
Thermal Exposure ◽  
Seasonal Temperature ◽  
Microbiome Composition ◽  
Desert Ant ◽  
Temperature Regimes ◽  
Response To Temperature

Microorganisms within ectotherms must withstand the variable body temperatures of their hosts. Shifts in host body temperature resulting from climate change have the potential to shape ectotherm microbiome composition. Microbiome compositional changes occurring in response to temperature in nature have not been frequently examined, restricting our ability to predict microbe-mediated ectotherm responses to climate change. In a set of field-based observations, we characterized gut bacterial communities and thermal exposure across a population of desert arboreal ants (Cephalotes rohweri). In a paired growth chamber experiment, we exposed ant colonies to variable temperature regimes differing by 5 C for three months. We found that the abundance and composition of ant-associated bacteria were sensitive to elevated temperatures in both field and laboratory experiments. We observed a subset of taxa that responded similarly to temperature in the experimental and observational study, suggesting a role of seasonal temperature and local temperature differences amongst nests in shaping microbiomes within the ant population. Bacterial mutualists in the genus Cephalotococcus (Opitutales: Opitutaceae) were especially sensitive to change in temperature - decreasing in abundance in naturally warm summer nests and warm growth chambers. We also report the discovery of a member of the Candidate Phlya Radiation (Phylum: Gracilibacteria), a suspected epibiont, found in low abundance within the guts of this ant species.

scholarly journals Zebrafish Polycomb repressive complex-2 critical roles are largely Ezh2- over Ezh1-driven and concentrate during early embryogenesis

2021 ◽  
Author(s):  
Gabriel A. Yette ◽  
Scott Stewart ◽  
Kryn Stankunas
Keyword(s):  
Cell Fate ◽  
Transcriptional Repression ◽  
Axial Skeleton ◽  
Early Embryogenesis ◽  
Loss Of Function ◽  
Allelic Series ◽  
Polycomb Repressive Complex ◽  
Genetic Studies ◽  
Polycomb Repressive Complex 2 ◽  
Early Developmental

ABSTRACTPolycomb repressive complex-2 (PRC2) methylation of histone H3 lysine-27 (H3K27me) is associated with stable transcriptional repression. PRC2 famously silences Hox genes to maintain anterior-posterior segment identities but also enables early cell fate specification, restrains progenitor cell differentiation, and canalizes cell identities. Zebrafish PRC2 genetic studies have focused on ezh2, which, with its paralog ezh1, encodes the H3K27 methyltransferase component. ezh2 loss-of-function mutants reinforce essential vertebrate PRC2 functions during early embryogenesis albeit with limited contributions to body plan establishment. However, redundancy with ezh1 and the lethality of maternal-zygotic homozygous ezh2 nulls could obscure additional early developmental and organogenesis roles of PRC2. Here, we combine new and existing zebrafish ezh1 and ezh2 alleles to show collective maternal/zygotic ezh2 exclusively provides earliest embryonic PRC2 H3K27me3 activity. Zygotic ezh1, which becomes progressively expressed as ezh2 levels dissipate, has minor redundant and noncompensatory larval roles but itself is not required for viability or fertility. Zygotic Ezh2/PRC2 promotes correct craniofacial bone shape and size by maintaining proliferative pre-osteoblast pools. An ezh2 allelic series including disrupted maternal ezh2 uncovers axial skeleton homeotic transformations and pleiotropic organogenesis defects. Further, once past a critical early window, we show zebrafish can develop near normally with minimal bulk H3K27me3. Our results suggest Ezh2-containing PRC2 stabilizes rather than instructs early developmental decisions while broadly contributing to organ size and embellishment.

scholarly journals Polycomb-group recruitment to a Drosophila target gene is the default state that is inhibited by a transcriptional activator

2021 ◽  
Vol 7 (29) ◽  
pp. eabg1556
Author(s):  
Elnaz Ghotbi ◽  
Piao Ye ◽  
Taylor Ervin ◽  
Anni Kum ◽  
Judith Benes ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Target Gene ◽  
Target Genes ◽  
De Novo ◽  
Polycomb Group ◽  
Polycomb Repressive Complex 2 ◽  
Repressive Chromatin ◽  
Group Recruitment ◽  
Default State ◽  
Present Experimental Evidence

Polycomb-group (PcG) proteins are epigenetic regulators that maintain the transcriptional repression of target genes following their initial repression by transcription factors. PcG target genes are repressed in some cells, but active in others. Therefore, a mechanism must exist by which PcG proteins distinguish between the repressed and active states and only assemble repressive chromatin environments at target genes that are repressed. Here, we present experimental evidence that the repressed state of a Drosophila PcG target gene, giant (gt), is not identified by the presence of a repressor. Rather, de novo establishment of PcG-mediated silencing at gt is the default state that is prevented by the presence of an activator or coactivator, which may inhibit the catalytic activity of Polycomb-repressive complex 2 (PRC2).

dCas9 targeted chromatin and histone enrichment for mass spectrometry (Catchet-MS) identifies IKZF1 as a novel drug-able target for HIV-1 latency reversal

2021 ◽  
Author(s):  
Enrico Ne ◽  
Raquel Crespo ◽  
Ray Izquierdo-Lara ◽  
Selin Kocer ◽  
Alicja Gorszka ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Transcriptional Repression ◽  
Host Factors ◽  
Hiv Cure ◽  
Polycomb Repressive Complex 2 ◽  
Infected Cells ◽  
Latent Hiv ◽  
Novel Drug ◽  
Enrichment Strategy ◽  
Hiv 1

SummaryA major pharmacological strategy toward HIV cure aims to reverse latency in infected cells as a first step leading to their elimination. While the unbiased identification of molecular targets physically associated with the latent HIV-1 provirus would be highly valuable to unravel the molecular correlates of HIV-1 transcriptional repression and latency reversal, due to technical limitations, this has not been possible. Here we use dCas9 targeted chromatin and histone enrichment strategy coupled to mass spectrometry (Catchet-MS) to isolate the latent and activated HIV-1 5’LTR, followed by MS identification of the differentially locus-bound proteins. Catchet-MS identified known and novel latent 5’LTR-associated host factors. Among these, IKZF1 is a novel HIV-1 transcriptional repressor, required for Polycomb Repressive Complex 2 recruitment to the LTR. We find the drug iberdomide, which targets IKZF1 for degradation, to be a clinically advanced novel LRA that reverses HIV-1 latency in CD4+T-cells isolated from virally suppressed HIV-1 infected participants.

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