Biology subjects

Keogh, M.-C.

Publications and source records attributed to Keogh, M.-C..

15 recordsLinked to original sources

bioRxiv2026

Spatially-resolved single cell atlas of liposarcoma reveals lineage hierarchies, immune niches, and regulatory circuits

Well-differentiated and dedifferentiated liposarcoma (WDLPS and DDLPS) exhibit markedly different clinical behaviors, with DDLPS showing greater aggressiveness, higher recurrence and metastasis rates, and worse outcomes. Using single-nucleus multiome sequencing, epigenomic profiling, and spatial transcriptomics, we characterized cellular and epigenetic heterogeneity between these subtypes at single-cell and spatial resolution. We found distinct phenotypic states reflecting altered lineage differentiation and plasticity: DDLPS is dominated by early-differentiated progenitor-like cells, sclerotic WDLPS displays broader mesenchymal lineage plasticity, and adipocytic WDLPS contains abundant committed adipocytes. The DDLPS immune microenvironment was dominated by immunosuppressive macrophages, whereas WDLPS harbored more T cells and inflammatory macrophages. Notably, sclerotic WDLPS displayed intermediate cellular and molecular features, suggesting it may represent a distinct WDLPS subtype. Importantly, we identified novel gene regulatory circuits underlying each state, including FABP4/PPARG programs in adipocytic WDLPS, GLI2/TCF7L2/RBPJ/KLF7 programs in sclerotic WDLPS, and KLF7/FOSL2/SP3/GLI2/RBPJ programs in DDLPS. H3K27ac-marked enhancers were enriched near adipocytic marker genes in WDLPS and mesenchymal markers in DDLPS. Together, these findings reveal the cellular heterogeneity of tumor and immune compartments across liposarcoma subtypes and identify regulatory programs driving their differentiation states. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/713651v1_ufig1.gif" ALT="Figure 1"> View larger version (73K): org.highwire.dtl.DTLVardef@1c84ee1org.highwire.dtl.DTLVardef@1b2ad42org.highwire.dtl.DTLVardef@18ce5a6org.highwire.dtl.DTLVardef@138f615_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2026

Different modes of engagement with the nucleosome acidic patch yield distinct functional outcomes

The nucleosome acidic patch is a hub of coordinated engagement by proteins that regulate genomic function. Here we report that S. cerevisiae Dot5 contains an arginine-rich HMGN-like motif that mediates nucleosome acidic patch binding and is required for the cell growth, DNA repair and heterochromatin defects exhibited when the protein is overexpressed. The heterologous expression of camelid single chain antibodies to the nucleosome acidic patch confers a similar range of phenotypes, with the most severe observed when an arginine-anchor mode of binding analogous to many endogenous factors is employed. This highlights a delicate balance between nucleosome acidic patch interactors critical for normal cellular functions and dysregulated in disease.

molecular biology↗

bioRxiv2025

Signaling induced biophysical disruption of repressed chromatin domains drives immune cell fate

Cell fate transitions require signal-induced chromatin derepression, yet mechanisms governing transitions from repressed to active chromatin states are poorly understood. We discover, at fate-defining genes across immune cell types, a signal-induced histone code, and describe domains of H3 serine 28 phosphorylation (H3S28ph) spanning architectural features, often coincident with repressive H3 lysine 27 trimethylation (H3K27me3). Employing biophysical, single cell, and functional approaches to study signal-induced cell differentiation in the immune system, we uncover epigenomic transitions and cell fate choices precipitated by histone phosphorylation (H3ph). Mechanistically, H3ph overrides Polycomb Repressive Complex 2 (PRC2) chromatin repression, biophysically disrupts polynucleosome compaction, and promotes loss of H3K27me3, while increasing activating H3K27 acetylation and H3K36 dimethylation to drive domain interactivity and stabilize transcription. We demonstrate the activity of H3ph in several cell fate transitions and illuminate biophysical mechanisms enabling rapid signal-activated chromatin derepression, processes with general relevance for cellular differentiation and activation.

immunology↗

bioRxiv2025

Heterochromatin fidelity is a therapeutic vulnerability in lymphoma and other human cancers

Genes involved in the regulation of chromatin structure are frequently disrupted in cancer, contributing to an aberrant transcriptome and phenotypic plasticity. Yet, therapeutics targeting mutant forms of chromatin-modifying enzymes have yielded only modest clinical utility, underscoring the difficulty of targeting the epigenomic underpinnings of aberrant gene regulatory networks. Here, we sought to identify novel epigenetic vulnerabilities in diffuse large B-cell lymphoma (DLBCL). Through phenotypic screens and biochemical analysis, we demonstrated that inhibition of the H3K9 demethylases KDM4A and KDM4C elicits potent, subtype-agnostic cytotoxicity by antagonizing transcriptional networks associated with B-cell identity and epigenetically rewiring heterochromatin. KDM4 demethylases associated with the KRAB zinc finger ZNF587, and their enzymatic inhibition led to DNA replication stress and DNA damage-induced cGAS-STING activation. Broad surveys of transcriptional data from patients also revealed KDM4 family dysregulation in several other cancer types. To explore this potential therapeutic avenue, we performed high-throughput small molecule screens with H3K9me3 nucleosome substrates and identified novel KDM4 demethylase inhibitors. AI-guided protein-ligand binding predictions suggested diverse modes of action for various small molecule hits. Our findings underscore the relevance of targeting fundamental transcriptional and epigenetic mechanisms for anti-cancer therapy. HIGHLIGHTSO_LIPhenotypic screens identified JIB-04 as a potent anti-cancer agent for multiple subtypes of diffuse large B-cell lymphoma C_LIO_LIJIB-04 binds and inhibits KDM4 demethylases resulting in epigenomic rewiring of heterochromatin C_LIO_LIKDM4 demethylases cooperate with KRAB zinc fingers to limit DNA replication stress, and KDM4 inhibition instigates DNA-damage and cGAS-STING activation in several human cancers C_LIO_LIHigh-throughput small molecule screens with semi-synthetic nucleosome substrates and AI-guided molecular docking simulations identify novel KDM4 inhibitors C_LI

genomics↗

bioRxiv2025

The conserved N-terminal SANT1-binding domain (SBD) of EZH2 Regulates PRC2 Activity

Polycomb group proteins maintain gene expression patterns established during early development, with Polycomb Repressive Complex 2 (PRC2) methyltransferase a key regulator of cell differentiation, identity and plasticity. Consequently, extensive somatic mutations in PRC2, including gain- or loss- of function (GOF or LOF), are observed in human cancers. The regulation of chromatin structure by PRC2 is critically dependent on its EZH2 (Enhancer of Zeste Homolog 2) subunit, which catalyzes the methylation of histone H3 lysine 27 (H3K27). Recent structural studies of PRC2 revealed extensive conformational changes in the non-catalytic EZH2 N-terminal SANT-Binding Domain (SBD) during PRC2 activation, though the functional significance remains unclear. Here, we investigate how the SBD regulates PRC2 function. The domain is highly conserved in metazoans, dispensable for PRC2 assembly and chromatin localization, yet required for genome-wide histone H3K27 methylation. Further, we show that an intact SBD is necessary for the proliferation of EZH2- addicted lymphomas, and its deletion in the presence of EZH2 GOF mutations inhibits cancer cell growth. These observations provide new insights to the regulation of PRC2 activity in normal development and malignancy.

genetics↗

bioRxiv2024

High-efficiency genomic mapping of chromatin-associated targets with CUT&RUN

The precise regulation of chromatin composition is critical to gene expression and cellular identity, and thus a key component in development and disease. Robust assays to study chromatin features, including histone post-translational modifications (PTMs) and chromatin-associated proteins (e.g., transcription factors or PTM readers), are essential to understand their function and identify novel therapeutic strategies. To this end, Cleavage Under Targets and Release Using Nuclease (CUT&RUN) has emerged as a powerful tool for high-resolution epigenomic profiling. The approach has been successfully applied to numerous cell and tissue types, informing on target genomic distribution with unprecedented sensitivity and throughput. Here, we provide a detailed CUT&RUN protocol from sample collection through data analysis, including best practices and defined controls to ensure specific, efficient, and robust target profiling.

genomics↗

bioRxiv2024

Histone H3 N-terminal recognition by the PHD finger of PHRF1 is required for proper DNA damage response

Plant homeodomain (PHD) fingers are critical effectors of histone post-translational modifications (PTMs), acting as regulators of gene expression and genome integrity, and frequently presenting in human disease. While most PHD fingers recognize unmodified and methylated states of histone H3 lysine 4 (H3K4), the specific functions of many of the over 100 PHD finger-containing proteins in humans remain poorly understood, despite their significant implications in disease processes. In this study, we undertook a comprehensive analysis of one such poorly characterized PHD finger-containing protein, PHRF1. Using biochemical, molecular, and cellular approaches, we show that PHRF1 robustly binds to histone H3, specifically at its N-terminal region. Through RNA-seq and proteomic analyses, we also find that PHRF1 is intricately involved in transcriptional and RNA splicing regulation and plays a significant role in DNA damage response (DDR). Crucially, mutagenesis of proline 221 to leucine (P221L) in the PHD finger of PHRF1 abolishes histone interaction and fails to rescue defective DDR. These findings underscore the importance of PHRF1-H3 interaction in maintaining genome integrity and provide insight into how PHD fingers contribute to chromatin biology.

biochemistry↗

bioRxiv2024

Ubiquitinated histone H2B as gatekeeper of the nucleosome acidic patch

Monoubiquitination of histones H2B-K120 (H2BK120ub) and H2A-K119 (H2AK119ub) play opposing roles in regulating transcription and chromatin compaction. H2BK120ub is a hallmark of actively transcribed euchromatin, while H2AK119ub is highly enriched in transcriptionally repressed heterochromatin. Whereas H2BK120ub is known to stimulate the binding or activity of various chromatin-modifying enzymes, this post-translational modification (PTM) also interferes with the binding of several proteins to the nucleosome H2A/H2B acidic patch via an unknown mechanism. Here we report cryoEM structures of an H2BK120ub nucleosome showing that ubiquitin adopts discrete positions that occlude the acidic patch. Molecular dynamics simulations show that ubiquitin remains stably positioned over this nucleosome region. By contrast, our cryoEM structures of H2AK119ub nucleosomes show ubiquitin adopting discrete positions that minimally occlude the acidic patch. Consistent with these observations, H2BK120ub, but not H2AK119ub, abrogates nucleosome interactions with acidic patch-binding proteins RCC1 and LANA, and single-domain antibodies specific to this region. Our results suggest a mechanism by which H2BK120ub serves as a gatekeeper to the acidic patch and point to distinct roles for histone H2AK119 and H2BK120 ubiquitination in regulating protein binding to nucleosomes.

biophysics↗

bioRxiv2022

An acetylation-mediated chromatin switch governs H3K4 methylation read-write capability

In nucleosomes, histone N-terminal tails exist in dynamic equilibrium between free/accessible and collapsed/DNA-bound states. The latter state is expected to impact histone N-termini availability to the epigenetic machinery. Notably, H3 tail acetylation (e.g., K9ac, K14ac, K18ac) is linked to increased H3K4me3 engagement by the BPTF PHD finger, but it is unknown if this mechanism has broader extension. Here we show that H3 tail acetylation promotes nucleosomal accessibility to other H3K4 methyl readers, and importantly, extends to H3K4 writers, notably methyltransferase MLL1. This regulation is not observed on peptide substrates yet occurs on the cis H3 tail, as determined with fully-defined heterotypic nucleosomes. In vivo, H3 tail acetylation is directly and dynamically coupled with cis H3K4 methylation levels. Together, these observations reveal an acetylation chromatin switch on the H3 tail that modulates read-write accessibility in nucleosomes and resolve the long-standing question of why H3K4me3 levels are coupled with H3 acetylation.

biochemistry↗

bioRxiv2022

Nucleosome conformation dictates the histone code

Histone post-translational modifications (PTMs) play a critical role in chromatin regulation. It has been proposed that these PTMs form localized codes that are read by specialized regions (reader domains) in chromatin associated proteins (CAPs) to regulate downstream function. Substantial effort has been made to define [CAP-histone PTM] specificity, and thus decipher the histone code / guide epigenetic therapies. However, this has largely been done using a reductive approach of isolated reader domains and histone peptides, with the assumption that PTM readout is unaffected by any higher order factors. Here we show that CAP-histone PTM interaction is in fact dependent on nucleosome context. Our results indicate this is due to histone tail accessibility and the associated impact on binding potential of reader domains. We further demonstrate that the in vitro specificity of a tandem reader for PTM-defined nucleosomes is recapitulated in a cellular context. This necessitates we refine the histone code concept and interrogate it at the nucleosome level.

genomics↗

bioRxiv2021

Arf6 anchors Cdr2 nodes at the cell cortex to control cell size at division

Fission yeast cells prevent mitotic entry until a threshold cell surface area is reached. The protein kinase Cdr2 contributes to this size control system by forming multiprotein nodes that inhibit Wee1 at the medial cell cortex. Cdr2 node anchoring at the cell cortex is not fully understood. Through a genomic screen, we identified the conserved GTPase Arf6 as a component of Cdr2 signaling. Cells lacking Arf6 failed to divide at a threshold surface area and instead shifted to volume-based divisions at increased overall size. Arf6 stably localized to Cdr2 nodes in its GTP-bound but not GDP-bound state, and its GEF (guanine nucleotide exchange factor) Syt22 was required for both Arf6 node localization and proper size at division. In arf6{Delta} mutants, Cdr2 nodes detached from the membrane and exhibited increased dynamics. These defects were enhanced when arf6{Delta} was combined with other node mutants. Our work identifies a regulated anchor for Cdr2 nodes that is required for cells to sense surface area.

cell biology↗

bioRxiv2021

Pharmacological targeting of a PWWP domain demonstrates cooperative control of NSD2 localization

NSD2 is the primary enzyme responsible for the dimethylation of lysine 36 of histone 3 (H3K36me2), a mark associated with active gene transcription and intergenic DNA methylation. In addition to a methyltransferase domain, NSD2 harbors two PWWP and five PHD domains believed to serve as chromatin reading modules, but their exact function in the regulation of NSD2 activity remains underexplored. Here we report a first-in-class chemical probe targeting the N-terminal PWWP (PWWP1) domain of NSD2. UNC6934 binds potently (Kd of 91 {+/-} 8 nM) to PWWP1, antagonizes its interaction with nucleosomal H3K36me2, and selectively engages endogenous NSD2 in cells. Crystal structures show that UNC6934 occupies the canonical H3K36me2-binding pocket of PWWP1 which is juxtaposed to the DNA-binding surface. In cells, UNC6934 induces accumulation of endogenous NSD2 in the nucleolus, phenocopying the localization defects of NSD2 protein isoforms lacking PWWP1 as a result of translocations prevalent in multiple myeloma. Mutation of other NSD2 chromatin reader domains also increases NSD2 nucleolar localization, and enhances the effect of UNC6934. Finally we identified two C-terminal nucleolar localization sequences in NSD2 that appear to drive nucleolar accumulation when one or more chromatin reader domains are disabled. These data support a model in which NSD2 chromatin engagement is achieved in a cooperative manner and subcellular localization is controlled by multiple competitive structural determinants. This chemical probe and the accompanying negative control, UNC7145, will be useful tools in defining NSD2 biology.

cell biology↗

bioRxiv2020

Separation and Characterization of Endogenous Nucleosomes by Native Capillary Zone Electrophoresis - Top-Down Mass Spectrometry (nCZE-TDMS)

We report a novel platform (native capillary zone electrophoresis - top-down mass spectrometry; nCZE-TDMS) for the separation and characterization of whole nucleosomes, their histone subunits, and PTMs. As the repeating unit of chromatin, mononucleosomes (Nucs) are a ~200 kDa complex of DNA and histone proteins involved in the regulation of key cellular processes central to human health and disease. Unraveling the covalent modification landscape of histones and their defined stoichiometries within Nucs helps to explain epigenetic regulatory mechanisms. In nCZE-TDMS, online Nuc separation is followed by a three-tier tandem MS approach that measures the intact mass of Nucs, ejects and detects the constituent histones, and fragments to sequence the histone. The new platform was optimized with synthetic Nucs to reduce both sample requirements and cost significantly compared to direct infusion. Limits of detection were in the low attomole range, with linearity over ~three orders of magnitude. The nCZE-TDMS platform was applied to endogenous Nucs from two cell lines distinguished by overexpression or knockout of histone methyltransferase NSD2/MMSET, where analysis of constituent histones revealed changes in histone abundances over the course of the CZE separation. We are confident the nCZE-TDMS platform will help advance nucleosome-level research in the fields of chromatin and epigenetics.

biochemistry↗

bioRxiv2020

Decoding the Protein Composition of Whole Nucleosomes with Nuc-MS

Nuc-MS characterizes histone modifications and variants directly from intact endogenous nucleosomes. Preserving whole nucleosome particles enables precise interrogation of their protein content, as for H3.3-containing nucleosomes which had 6-fold co-enrichment of variant H2A.Z over bulk chromatin. Nuc-MS, validated by ChIP-seq, showed co-occurrence of oncogenic H3.3K27M with euchromatic marks (e.g., H4K16ac and >15-fold enrichment of H3K79me2). By capturing the entire epigenetic landscape, Nuc-MS provides a new, quantitative readout of nucleosome-level biology.

biochemistry↗

bioRxiv2020

Screening of PCRP transcription factor antibodies in biochemical assays

Antibodies offer a powerful means to interrogate specific proteins in a complex milieu. However, antibody availability and reliability are problematic and epitope tagging can be impractical in many cases. In an effort to improve this situation, the Protein Capture Reagents Program (PCRP) generated over a thousand renewable monoclonal antibodies (mAbs) against human-presumptive chromatin proteins. However, these reagents have not been widely field-tested. We therefore performed a screen to test their ability to enrich genomic regions via chromatin immunoprecipitation (ChIP) and a variety of orthogonal assays. 887 unique antibodies against 681 unique human transcription factors (TFs), were assayed by ultra-high resolution ChIP-exo/seq, primarily in a single pass in one cell type (K562). Deep systematic analyses of the resulting [~]1,200 ChIP-exo datasets can be found at www.PCRPvalidation.org. Subsets of PCRP mAbs were further tested in ChIP-seq, CUT&RUN, STORM super-resolution microscopy, immunoblots, and protein binding microarray (PBM) experiments. About 5% of the tested antibodies displayed target (i.e., cognate antigen) enrichment across at least one assay and are strong candidates for additional validation. An additional 34% produced ChIP-exo data that was distinct from background and thus warrant further testing. The remaining 61% were not substantially different from background, and likely require consideration of a much broader survey of cell types and/or assay optimizations. We demonstrate and discuss the metrics and challenges to antibody validation in chromatin-based assays.

biochemistry↗