Biology subjects

Conway, E.

Publications and source records attributed to Conway, E..

6 recordsLinked to original sources

bioRxiv2026

Divergent Pathogenic PR-DUB Complex Variants Converge Functionally Via PRC2 Displacement From Chromatin

The PR-DUB complex is responsible for erasing the repressive histone modification, H2AK119ub1. ASXL1-3 proteins are mutually exclusive catalytic partners of BAP1 in the PR-DUB complex. Somatic heterozygous ASXL1-3 variants are associated with cancer, including myeloid malignancies, while de novo germline variants cause neurodevelopmental disorders such as Bohring-Opitz syndrome. These pathogenic variants are almost exclusively nonsense and frameshift and have been proposed to act as gain-of-function. However, the precise catalytic impact and mechanism of variant ASXL1-3 remains elusive. Using an isogenic embryonic stem cell model we have discovered that ASXL1 BOS variants drive reductions - but not global ablations - in H2AK119ub1, consistent with gain-of-function. This catalytic change occurs through the production of a truncated ASXL1 protein with enhanced stability. Hyper-stabilised ASXL1 drives a stoichiometric shift in PR-DUB assembly away from ASXL2 complexes. The drop in H2AK119ub1 levels ultimately reduces PRC2 binding and H3K27me3 deposition. Surprisingly, this phenotype is shared across PR-DUB loss-of-function models and indeed is emerging as a common phenotype across genetically and mechanistically distinct Polycomb-related chromatinopathies.

genetics↗

bioRxiv2025

AEBP2-Directed H3K27me2 Defines a Specific Vulnerability in EZH2-mutant Lymphoma

The catalytic subunit of Polycomb Repressive Complex 2 (PRC2), EZH2, is recurrently mutated in 25% of diffuse large B-cell lymphomas (DLBCL), causing increased H3K27me3 and decreased H3K27me2 levels. EZH2 inhibitors provide clinical benefit, but resistance frequently develops, highlighting the need for alternative therapeutic targets. Here, we identify the PRC2 accessory protein AEBP2 as a specific genetic dependency in EZH2-mutant DLBCL. While AEBP2 acts through PRC2, its essential role is surprisingly independent of canonical H3K27me3-mediated gene silencing. Instead, AEBP2 functions within a PRC2.2 complex lacking JARID2, using its zinc-finger domains to sample intergenic chromatin to sustain H3K27me2. Notably, loss of AEBP2 or NSD2 caused contrasting changes in intergenic H3K27me2 levels, driving sensitivity or resistance to PRC2 inhibitors, respectively. Our findings identify AEBP2-PRC2.2-maintained intergenic H3K27me2 as a therapeutic vulnerability in EZH2-mutant DLBCL and highlight dysregulated H3K27me2 as an underappreciated form of PRC2 dysfunction in cancer, with important therapeutic implications.

cancer biology↗

bioRxiv2023

Dominant negative and directional dysregulation of Polycomb function in EZH2-mutant human growth disorders

Heterozygous missense mutations in EZH2 cause Weaver syndrome (WS), a developmental disorder characterized by intellectual disability and overgrowth. EZH2 encodes the enzymatic subunit of Polycomb Repressive Complex 2 (PRC2), which mediates mono-, di-, and tri-methylation of histone H3 lysine residue 27 (H3K27me1/2/3). Although the functional characterization of most WS-associated EZH2 variants is lacking, they are presumed loss of function. However, the dearth of reported early truncating mutations in EZH2 led us to hypothesise that a dominant negative mutational mechanism may underlie the development of WS. To test this, we performed a detailed structural analysis of all known WS-associated EZH2 variants, which provided initial support that they are dominant negative. Next, we isogenically modelled 10 representative WS-associated EZH2 variants in embryonic stem cells and showed they induce global reductions in H3K27me2 and H3K27me3 with concomitant global increases in H3K27me1, H3K27ac, and chromatin decompaction. Importantly, the reductions in H3K27me2/3 methylation revealed a pattern of dominant-negative interference to PRC2 activity. Comparative analysis of a gain-of-function EZH2 variant causing growth restriction highlighted the reciprocal nature of the chromatin changes in these opposing growth syndromes. Our findings detail the molecular effects of developmental-syndrome-associated EZH2 variants in cells and implicate imbalanced landscapes of H3K27 modification in their pathology.

genetics↗

bioRxiv2022

Maternal and/or direct supplementation with a combination of a casein hydrolysate and yeast β-glucan on post-weaning performance and intestinal health in the pig

A 2 x 2 factorial experiment was conducted to investigate the effect of maternal supplementation from day 83 of gestation and/or direct supplementation from weaning of a bovine casein hydrolysate plus a yeast {beta}-glucan (CH-YBG) on pig performance and intestinal health on day ten post-weaning. Twenty cross bred gilts (Large White x Landrace) were randomly assigned to one of two dietary groups (n = 10 gilts/group): basal diet (basal sows) and basal diet supplemented with CH-YBG (supplemented sows) from day 83 of gestation until weaning (2g/sow/day). At weaning, 120 pigs (6 pigs/sow) were selected. The two dam groups were further divided, resulting in four experimental groups (10 replicates/group; 3 pigs/pen) as follows: 1) BB (basal sows + basal pigs); 2) BS (basal sows + supplemented pigs); 3) SB (supplemented sows + basal pigs); 4) SS (supplemented sows + supplemented pigs). Supplemented pigs were offered 0.5g CH-YBG/kg of feed for 10 days post-weaning. On day 10 post-weaning, 1 pig/pen was humanely sacrificed and samples were taken from the gastrointestinal tract for analysis. Pigs weaned from supplemented sows (SS, SB) had reduced faecal scores and incidence of diarrhoea (P<0.05) compared to pigs weaned from basal sows (BB, BS), with SS pigs not displaying the transient rise in faecal scores seen in the other three groups from day 3 to day 10 post-weaning (P<0.05). Pigs weaned from supplemented sows had reduced feed intake (P<0.05), improved feed efficiency (P<0.05), increased butyrate concentrations (P<0.05), increased abundance of Lactobacillus (P<0.05) and decreased abundance of Enterobacteriaceae and Campylobacteraceae (P<0.05) compared to pigs weaned from basal sows. In conclusion, a combination of both maternal and direct supplementation with CH-YBG is the desirable feeding strategy to ameliorate the post-weaning challenge in pig production systems.

developmental biology↗

bioRxiv2020

BAP1 activity regulates PcG occupancy and global chromatin condensation counteracting diffuse PCGF3/5-dependent H2AK119ub1 deposition

BAP1 is recurrently mutated or deleted in a large number of diverse cancer types, including mesothelioma, uveal melanoma and hepatocellular cholangiocarcinoma. BAP1 is the catalytic subunit of the Polycomb Repressive De-Ubiquitination complex (PR-DUB) which removes PRC1 mediated H2AK119ub1. We and others have shown that H2AK119ub1 is essential for maintaining transcriptional repression and contributes to PRC2 chromatin recruitment. However, the precise relationship between BAP1 and PRC1 remains mechanistically elusive. Using embryonic stem cells, we show that a major function of BAP1 is to restrict H2AK119ub1 deposition to target sites. This increases the stability of PcG complexes with their targets and prevents diffuse accumulation of H2AK119ub1 and H3K27me3 modifications. Loss of BAP1 results in a broad increase in H2AK119ub1 levels that are primarily dependent on PCGF3/5-PRC1 complexes with a mechanism that is reminiscent of X-chromosome inactivation. Increased genome-wide H2AK119ub1 levels titrates away PRC2 from its targets and stimulates diffuse H3K27me3 accumulation across the genome. This decreases the activity of PcG repressive machineries at physiological targets and induces a general compaction of the entire chromatin. Our findings provide evidences for a unifying model that resolves the apparent contradiction between BAP1 catalytic activity and its role in vivo, uncovering molecular vulnerabilities that could be useful for BAP1-related pathologies.

molecular biology↗

bioRxiv2019

Histone H2AK119 Mono-Ubiquitination is Essential for Polycomb-Mediated Transcriptional Repression

The major function of Polycomb group proteins (PcG) is to maintain transcriptional repression to preserve cellular identity. This is exerted by two distinct repressive complexes, PRC1 and PRC2, that modify histones by depositing H2AK119ub1 and H3K27me3, respectively. Both complexes are essential for development and are deregulated in several types of human tumors. PRC1 and PRC2 exist in different variants and show a complex regulatory cross-talk. However, the contribution that H2AK119ub1 plays in mediating PcG repressive functions remains largely controversial. Coupling an inducible system with the expression of a fully catalytic inactive RING1B mutant, we demonstrated that H2AK119ub1 deposition is essential to maintain PcG-target genes repressed in ESC. Loss of H2AK119ub1 induced a rapid displacement of PRC2 activity and a loss of H3K27me3 deposition. This affected both PRC2.1 and PRC2.2 variants and further correlated with a strong displacement and destabilization of canonical PRC1. Finally, we find that variant PRC1 forms can sense H2AK119ub1 deposition, which contributes to their stabilization specifically at sites where this modification is highly enriched. Overall our data place H2AK119ub1 deposition as central hub that mount PcG repressive machineries to preserve cell transcriptional identity.

molecular biology↗