Biology subjects

Jayavelu, A. K.

Publications and source records attributed to Jayavelu, A. K..

4 recordsLinked to original sources

bioRxiv2026

BAF complex-independent gene activation by SS18::SSX

In synovial sarcoma, the BAF subunit SS18 is fused to SSX, a transcriptional repressor, generating the oncogenic SS18::SSX fusion protein. Incorporation of SS18::SSX into BAF complexes leads to their aberrant retargeting to Polycomb-repressed genes via SSX, while simultaneously altering their composition and activity. The presence of BAF at Polycomb target sites is widely assumed to be essential for gene activation. Here, we directly tested the requirement for BAF activity in synovial sarcoma cell survival and SS18::SSX-driven transcription. Using targeted degradation of BAF ATPase subunits and deletion of core components, we show that BAF loss has modest effects on sarcoma cell viability and does not impede SS18::SSX target gene expression. Consistently, deletion of the BAF ATPase subunit Smarca4 does not impair SS18::SSX-driven tumor formation in vivo. Using domain-specific SS18::SSX mutants, we further demonstrate that the fusion can activate oncogenic transcription independently of BAF interaction, and that this activity depends on the C-terminal QPGY-rich domain of SS18. Mechanistically, SS18::SSX promotes transcription by engaging the histone acetyltransferase EP300, independently of BAF. Accordingly, pharmacologic degradation of EP300/CREBBP suppresses SS18::SSX-driven transcriptional programs and impairs synovial sarcoma cell survival. Together, these findings challenge the view that BAF activity is required for SS18::SSX-mediated transcriptional activation and demonstrate that aberrant Polycomb target gene expression is sustained through recruitment of transcriptional coactivators in the absence of BAF. Our work reveals new therapeutic vulnerabilities in synovial sarcoma and suggests broader relevance for targeting coactivator-dependent transcription in fusion-driven cancers. HighlightsO_LIBAF degradation does not alter SS18::SSX-activated transcriptional programs C_LIO_LIDirect SS18::SSX transcriptional activation is independent of BAF interaction C_LIO_LIThe SS18 C-terminus engages the co-activator EP300 to promote gene expression C_LIO_LISmall molecule degraders of EP300/CREBBP abolish SS18::SSX-mediated transcription C_LI

cancer biology↗

bioRxiv2025

Sodium Aurothiomalate Induces Ferroptosis by Targeting GPX4 via Gold-Dependent Thiomalate Covalent Modification

Ferroptosis, an iron-dependent form of oxidative cell death, is predominantly regulated by glutathione peroxidase 4 (GPX4), making it a promising target for cancer therapy. However, the majority of GPX4 inhibitors, most of which contain a chloroacetamide moiety such as RSL3, are limited by poor pharmacokinetic properties and off-target effects, hindering their preclinical translation. Utilizing a range of interdisciplinary methodologies, we show that sodium aurothiomalate (ATM), a drug approved by many agencies, induces ferroptosis by covalently targeting GPX4 via formation of a selenenylsulfide bond. In preclinical models of neuroblastoma and acute myeloid leukemia (AML), ATM combined with ferric ammonium citrate (FAC) yields a synergistic effect, resulting in a significant reduction in tumor growth. Mechanistically, ATM disrupts GPX4 activity by covalently binding thiomalate to the active site selenocysteine, while modification of specific cysteine residues leads to destabilization of the protein and impaired binding to phospholipids. We propose that these covalent modifications are achieved through a unique reaction mechanism, in which the gold component of ATM acts as a thiol-masking carrier and is only transiently present, being subsequently displaced and allowing the reaction of the thiomalate moiety with the target selenocysteine or cysteine. Our data lay the foundation for development of novel, drug-like thiol-based GPX4 inhibitors.

biochemistry↗

bioRxiv2025

cIAP1 inhibitor of apoptosis is a tumor suppressor in Ewing sarcoma

Ewing sarcoma (EwS) is a highly aggressive pediatric malignancy driven by EWSR1::ETS fusion oncoproteins -primarily EWSR1::FLI1- which deregulate genes essential for differentiation, proliferation, and cell survival. To uncover key downstream targets of this fusion involved in cell differentiation, we combined transcriptomic profiling of EwS cell lines following EWSR1::FLI1 inhibition with gene ontology analysis, a clinically annotated gene expression dataset derived from EwS patient material and network analyses. This integrative approach identified inhibitor of apoptosis protein 1 (cIAP1, alias BIRC2) as an EWSR1::FLI1-suppresed gene. Despite its known oncogenic role in many cancers, cIAP1 showed minimal expression in EwS. Using inducible cIAP1 re-expression models in EwS cells, we demonstrated that cIAP1 re-expression suppresses proliferation, clonogenic growth, and 3D spheroid formation in vitro. Transcriptomic and proteomic analyses revealed that low cIAP1 expression enhances proliferation-related gene signatures, which are inhibited upon cIAP1 re-expression. In vivo xenograft models revealed that cIAP1 re-expression significantly reduces tumor growth, mitotic activity, and Ki-67 positivity, while increasing tumor necrosis and apoptosis. These findings highlight an unexpected tumor-suppressive role for cIAP1 in fusion-driven sarcomas, contrasting with its pro-survival function in other cancers. Collectively, our results identify cIAP1 as a prognostically relevant, EWSR1::FLI1-regulated hub whose re-expression disrupts tumor progression, offering a potential therapeutic strategy to restore tumor-suppressive pathways in EwS.

cancer biology↗

bioRxiv2024

EasyAb: A High-Throughput Workflow for Antibody-Based PTM Peptide Enrichment Method Coupled to Mass Spectrometry

Reversible post-translational modification (PTMs) is a fundamental mechanism of cellular signal transduction. In vivo and ex vivo studies to profile PTMs have greatly advanced our understanding of the complexities of cellular signaling. However, apart from the most commonly studied PTMs, large-scale analysis is still very challenging, limiting our understanding of various cellular processes. PTM-bearing peptides often enriched by antibodies, followed by unbiased mass spectrometry (MS)-based readout of hundreds or thousands of sites. To extend the reach of this powerful technology to in vivo and ex vivo studies with small protein starting amounts, we here developed EasyAb, a streamlined and high throughput MS workflow for antibody-based PTM profiling. Using epidermal growth factor receptor (EGFR) signaling and acute myeloid leukemia (AML) cell systems, we demonstrate that EasyAb increases sensitivity and enables multiple large-scale systems-level studies. Furthermore, EasyAb resolves in vivo brain G protein-coupled receptor-mediated tyrosine kinase activation and reveals the long elusive hypothalamic neuron-specific leptin signaling architecture. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=125 SRC="FIGDIR/small/620939v1_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@259537org.highwire.dtl.DTLVardef@1675a43org.highwire.dtl.DTLVardef@570b61org.highwire.dtl.DTLVardef@ac45df_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSEasyAb, a sensitive, rapid and high-throughput method to quantify post translationally modified peptides in diverse cell systems. EasyAb reveals differential tyrosine phosphorylation of mRNA splicing proteins in AML patient samples. Activation of KOR by "G-protein-biased" non-aversive agonist 6GNTI elicits Src kinase activity in mice. Elucidation of in vivo hypothalamic Leptin induced LEPRb-Jak2 phosphotyrosine signaling architecture.

biochemistry↗