Biology subjects

Choudhary, J. S.

Publications and source records attributed to Choudhary, J. S..

At least 19 recordsLinked to original sources

bioRxiv2026

Engineering and characterisation of AAVS1 FRT cell lines for inducible and dose-dependent gene expression

Investigating biological function with high reproducibility requires the generation of stable cell lines that offer precise and inducible transgene expression. However, traditional methods often suffer from the limitations of random genomic integration, including unpredictable expression levels, leaky basal activity, and disruption of endogenous loci. To address these challenges, we engineered a versatile RPE1 cell line by integrating a TetOn3G-FRT cassette into the AAVS1 safe-harbour locus using CRISPR/Cas9(D10A) nickase. This platform utilises the Flp-FRT recombination system to facilitate rapid, site-specific "plug-and-play" insertion of transgenes, combined with the Tet-On 3G system for tight, dose-dependent expression control. The resulting RPE1 AAVS1 FRT8 line enables highly consistent transgene induction across independent clones, behaving as a monoclonal population. We highlight the importance of rigorous cell line characterisation through a multi-omics approach. Whole genome sequencing identified precise heterozygous integration at the target locus and de novo genomic duplications on other chromosomes. By integrating WGS with high-resolution proteomics and cell cycle analysis, we confirmed that these alterations did not significantly perturb cellular homeostasis or phenotypic fitness. This work establishes a robust and reliable platform for the efficient generation of inducible AAVS1 FRT stable cell lines, facilitating reproducible research in modern molecular biology.

bioengineering↗

bioRxiv2026

Rapid early degradation of Cyclin A is important to maintain genomic stability

The Anaphase Promoting Complex/Cyclosome (APC/C) ubiquitin ligase controls mitosis by targeting the mitotic Cyclins for degradation. At Nuclear Envelope Breakdown the APC/C immediately targets CyclinA but the Spindle Assembly Checkpoint prevents it recognising CyclinB until all chromosomes have attached to the mitotic apparatus. The degradation of CyclinA before CyclinB is conserved in evolution but the physiological role of this is not yet clearly established. Overexpressing CyclinA or a non-degradable mutant interferes with chromosome congression and promotes microtubule instability, but the effect of delaying the degradation of endogenous CyclinA has not been determined. Here, we mutated two APC/C-recognition motifs in human CyclinA2 to slow down its degradation. We find that slower degradation of CyclinA alters microtubule dynamics and induces errors in chromosome congression and chromosome clustering at mitotic exit, leading to aneuploidy and malformed daughter cell nuclei. We identify Ki67 as the candidate to interfere with chromosome clustering since its phosphorylation and behaviour are perturbed when CyclinA is degraded more slowly. We conclude that rapid early CyclinA degradation is important for genomic stability.

cell biology↗

bioRxiv2026

Structural basis of polyspecific drug recognition by MRP2

Multidrug resistance-associated protein 2 (MRP2/ABCC2) is a hepatobiliary ATP-binding cassette transporter that mediates the efflux of endogenous conjugates and many therapeutic agents, yet the basis of its broad ligand specificity remains poorly understood. Here we combine cryo-electron microscopy, ATPase measurements and cell-based transport inhibition assays to define how MRP2 recognizes clinically relevant compounds from distinct chemical classes. We find that chemically diverse ligands occupy overlapping regions of a shared transmembrane cavity but adopt different poses, contact networks and stoichiometries. Ligand recognition is mediated predominantly by a permissive environment complemented by ligand-specific polar interactions, rather than by a single conserved pharmacophore. These findings establish a structural framework for MRP2 polyspecificity and provide insight into hepatobiliary drug disposition and transporter-mediated drug-drug interactions.

biochemistry↗

bioRxiv2026

Cryo-EM structures of the CDK11-cyclin L-SAP30BP complex reveal mechanisms of CDK11 regulation

The cyclin-dependent kinase CDK11 functions in transcription, mitotic progression, and mRNA splicing. Specifically, spliceosome activation during the B to Bact transition depends on phosphorylation of the U2 snRNP component SF3B1 by the CDK11-cyclin L-SAP30BP complex. Here, we present the structure of this spliceosome-activating CDK-cyclin complex, determined by cryogenic electron microscopy at 2.3 [A] resolution. Our structure and biochemical experiments show that SAP30BP forms extensive interactions with cyclin L2, thereby stabilising it, and forms critical interactions with the C-terminal kinase lobe of CDK11 that promote complex assembly. Destabilisation of cyclin L2 in the absence of SAP30BP suggests that these principles are applicable to all CDK11-cyclin L complexes. Furthermore, we identify a pseudo-substrate sequence near the CDK11 C-terminus and provide evidence for a role of this segment in CDK11 auto-regulation. Finally, the structure of the CDK11-cyclin L2-SAP30BP complex bound to the clinical high-affinity CDK11 inhibitor OTS964 and a comparison to OTS964-bound off-target complexes provide insight into the mechanism of OTS964 selectivity and specificity.

molecular biology↗

bioRxiv2026

High resolution interaction surface mapping by PRISMA reveals novel ARID1A interactions

The SWI/SNF chromatin remodelling complex controls proliferation and cell fate determination by regulating chromatin accessibility at promoters and enhancers, thereby modulating programs of gene expression, and has roles in DNA damage response, replication, splicing, and translation, and cell plasticity. The cBAF-exclusive subunit ARID1A acts as scaffold for the assembly of cBAF SWI/SNF complexes through its C-terminal globular domain and is the most frequently mutated SWI/SNF subunit in cancer. More than half of the ARID1A protein sequence contains regions of intrinsic disorder which are important for protein interactions, often mediated by short linear motifs. However, these interactions are notoriously difficult to study. Whilst hundreds of ARID1A interactions have been reported in the literature, their molecular basis remains obscure, and only a few have been explored functionally or mapped at an interface level. Here, we use a PRotein Interaction Screen on a peptide MAtrix (PRISMA) combined with quantitative mass spectrometry to identify novel ARID1A interactions and map amino acid residues and motifs that mediate interactions at high sequence resolution. The ARID1A PRISMA assay recapitulates binding of BAF subunits to ARID1A and detects the previously described binding of YAP1 transcriptional coactivator to a PPXY motif. Our PRISMA data reveals binding sites for transcriptional repressor SIN3A and identifies TOX4, CDK2 and CCNA2 as novel interactors. Mutation of a cell cycle-dependent CDK2 phosphorylation site in ARID1A leads to altered gene expression of microtubule factors and defects in cell proliferation. Our work underscores the utility of PRISMA to uncover weak or low abundance interactions that are not detectable by traditional affinity purification strategies. Together, our results characterise novel interactors and a new mode of regulation of ARID1A, and provide a useful resource to further explore mechanistic aspects of ARID1A function.

biochemistry↗

bioRxiv2025

LOX inhibition disrupts a collagen-integrin-MYC axis as a translatable targeting strategy in invasive lobular carcinoma

Invasive lobular carcinoma (ILC) accounts for 15% of breast cancers yet lacks specific therapy because ILCs are underrepresented in clinical trials and preclinical models are lacking. We established intraductal xenograft models to test whether the clinical pan-lysyl-oxidase PXS-5505, now in phase trials for myelofibrosis can exploit the collagen-rich matrix dependency created by CDH1 loss. PXS-5505 remodels fibrillar collagen, and halts tumor expansion and metastatic seeding across ER+ and triple negative models without systemic toxicity. Genome-wide CRISPR screens reveal ITGAV and ITGB5 as synthetic lethal partners of CDH1 and LOX inhibition downregulates their expression together with MYC, NF-{kappa}B, and AP-1 transcriptional programmes. Collagen fibre density/alignment, and MYC/AP-1 gene signatures serve as pharmacodynamic readouts of drug activity. These data uncover a tractable ECM-integrin-MYC axis in ILC and nominate PXS-5505, alone or with endocrine therapy, for window of opportunity trials in this understudied breast cancer subtype. One Sentence SummaryTargeting matrix remodelling in ILC inhibits ILC progression and alters multiple molecular endpoints, providing a translatable therapeutic strategy for this understudied subtype that requires better treatments.

cancer biology↗

bioRxiv2025

An expanded reference catalog of translated open reading frames for biomedical research

Non-canonical (i.e., unannotated) open reading frames (ncORFs) have until recently been omitted from reference genome annotations, despite evidence of their translation, limiting their incorporation into biomedical research. To address this, in 2022, we initiated the TransCODE consortium and built the first community-driven consensus catalog of human ncORFs, which was openly distributed to the research community via Ensembl-GENCODE. While this catalog represented a starting point for reference ncORF annotation, major technical and scientific issues remained. In particular, this initial catalogue had no standardized framework to judge the evidence of translation for individual ncORFs. Here, we present an expanded and refined catalog of the human reference annotation of ncORFs. By incorporating more datasets and by lifting constraints on ORF length and start-codon, we define a comprehensive set of 28,359 ncORFs that is nearly four times the size of the previous catalog. Furthermore, to aid users who wish to work with ncORFs with the strongest and most reproducible signals of translation, we utilized a data-driven framework (i.e. translation signature scores) to assess the accumulated evidence for any individual ncORF. Using this approach, we derive a subset of 7,888 ncORFs with translation evidence on par with canonical protein-coding genes, which we refer to as the Primary set. This set can serve as a reliable reference for downstream analyses and validation, with a particular emphasis on high quality. Overall, this update reflects continual community-driven efforts to make ncORFs accessible and actionable to the broader research public and further iterations of the catalog will continue to expand and refine this resource.

genomics↗

bioRxiv2025

MAGELLAN: Automated Generation of Interpretable Computational Models for Biological Reasoning

Computational models have become essential tools for understanding signalling networks and their non-linear dynamics. However, these models are typically constructed manually using prior knowledge and can be over-reliant on study bias. These limitations hinder their ability to make accurate predictions and incorporate new evidence. Scaling up the construction of models to take advantage of increasingly abundant omics data can bridge these gaps by providing a comprehensive view of signalling events and how they influence cellular phenotypes. In this study, we present MAGELLAN, a method leveraging message passing graph neural networks to build computational models directly from pathway data and discrete rules representing experimental results. We used this to construct a computational model of breast cancer signalling and re-parameterize a previously published non-small cell lung cancer (NSCLC) model, showing that MAGELLAN can predict genetic dependencies and achieve comparable model quality to expert-curated and manually trained models. Our approach enables the integration of prior knowledge networks and experimental data to build predictive models that are mechanistically interpretable. This approach simplifies model creation, making it more accessible and practical for experimentalists, and supports broader applications in drug discovery and biological research.

systems biology↗

bioRxiv2025

The accessory type III secretion system effectors shape intestinal inflammatory infection outcomes

Injection of effectors via a type III secretion system (T3SS) is an infection strategy shared by various Gram-negative bacterial pathogens, many infecting mucosal surfaces. While individual T3SS effectors are well characterized, their network-level organization and the distinction between core and accessory effectors remain incompletely understood. Here, by systematically dissecting the T3SS effector network of the enteric mouse pathogen Citrobacter rodentium (CR) we identified a subset of 12 accessory effectors that, while dispensable for colonization, significantly alter infection outcomes. A strain lacking the accessory effectors (CRM12) remained virulent in susceptible mouse hosts yet resulted in reduced epithelial barrier damage, inflammation, and immune cell infiltration in resistant mice. Deep proteomic analysis specifically targeting CR-attached colonic epithelial cells revealed that, despite lacking 39% of its effector repertoire, infection with CRM12 results in similar changes to global protein expression as seen in mice infected with the wild-type strain, though key regulators of barrier integrity were differentially expressed. Using a host model with impaired barrier repair, we confirmed that accessory effectors shape infection outcomes without significantly impacting virulence. This study refines the concept of core and accessory effectors, providing a basis for further studies into effector-driven host adaptation.

microbiology↗

bioRxiv2024

Chromosome end protection by RAP1-mediated inhibition of DNA-PK

During classical non-homologous end joining (cNHEJ), DNA-dependent protein kinase (DNA-PK) encapsulates free DNA ends, forming a recruitment platform for downstream end-joining factors including Ligase 4 (LIG4)1. DNA-PK can also bind telomeres and regulate their resection2-4, but does not initiate cNHEJ at this position. How the end joining process is regulated in this context-specific manner is currently unclear. Here we show that the shelterin components TRF2 and RAP1 form a complex with DNA-PK that directly represses its end joining function at telomeres. Biochemical experiments and cryo-electron microscopy reveal that when bound to TRF2, RAP1 establishes a network of interactions with KU and DNA that prevents DNA-PK from recruiting LIG4. In mouse and human cells, RAP1 is redundant with the Apollo nuclease in repressing cNHEJ at chromosome ends, demonstrating that the inhibition of DNA-PK prevents telomere fusions in parallel with overhang-dependent mechanisms. Our experiments show that the end joining function of DNA-PK is directly and specifically repressed at telomeres, establishing a molecular mechanism for how individual linear chromosomes are maintained in mammalian cells.

biochemistry↗

bioRxiv2024

Cell cycle-dependent S-sulfenyl proteomics uncover a redox switch in p21-CDK feedback governing the proliferation-senescence decision

Reactive oxygen species (ROS) influence cell proliferation and fate decisions by oxidizing cysteine residues (S-sulfenylation) of proteins, but specific targets and underlying regulatory mechanisms remain poorly defined. Here, we employ redox proteomics to identify cell cycle-coordinated S-sulfenylation events and investigate their functional role in proliferation control. Although ROS levels rise during cell cycle progression, overall oxidation of the proteome remains constant with dynamic S-sulfenylation restricted to a subset of cysteines. Among these, we identify a critical redox-sensitive cysteine residue (C41) in the cyclin-dependent kinase (CDK) inhibitor p21. C41 oxidation regulates the interaction of p21 with CDK2 and CDK4, controlling a double-negative feedback loop that determines p21 stability. When C41 remains reduced, p21s half-life increases in G2 phase resulting in more p21 inheritance to daughter cells suppressing proliferation and promoting senescence after irradiation. Notably, we identify dynamic S-sulfenylation on further cell cycle regulators implying coordination of cell cycle and redox control.

cell biology↗

bioRxiv2024

PBRM1 directs PBAF to pericentromeres and protects centromere integrity

The specialised structure of the centromere is critical for effective chromosome segregation, but its repetitive nature makes it vulnerable to rearrangements. Centromere fragility can drive tumorigenesis, but protective mechanisms preventing fragility are still not fully understood. The PBAF chromatin remodelling complex is frequently misregulated in cancer, but its role in cancer is still not fully characterized. Here, we identify PBAF as a protector of centromere and pericentromere structure with profound consequences for genome stability. A conserved feature of isogenic cell lines lacking PBRM1, a subunit of PBAF, is compromised centromere and pericentromere integrity. PBAF is present at these regions, and the binding pattern changes when PBRM1 is absent. PBRM1 loss creates a dependence on the spindle assembly checkpoint, which represents a therapeutic vulnerability. Importantly, we find that even in the absence of any perturbations, PBRM1 loss leads to centromere fragility, thus identifying a new player in centromere protection.

molecular biology↗

bioRxiv2023

Systematic screens for fertility genes essential for malaria parasite transmission reveal conserved aspects of sex in a divergent eukaryote

Sexual reproduction in malaria parasites is essential for their transmission to mosquitoes. It also offers a divergent eukaryote model to understand the evolution of sex. Through a panel of genetic screens, where each sex of Plasmodium berghei was mutagenised separately with barcoded vectors, we identify 401 sex and transmission-related gene functions and define roles for hundreds of unstudied fertility genes as putative targets for transmission blocking interventions. The functional data provide a deeper understanding of female metabolic reprogramming, meiosis and the axoneme. We identify a protein complex of a SUN domain protein, SUN1, and a moonlighting putative allantoicase, ALLC1, that is essential for male fertility by linking the microtubule organising centre to the nuclear envelope and enabling mitotic spindle formation during male gametogenesis. Both proteins have orthologs in mouse testis, and the data point to an ancient role for atypical SUN domain proteins in fertility. Altogether, our data provide an unbiased picture of the molecular processes that underpin malaria parasite transmission but also highlight ancestral aspects of sex that have evolved close to the last eukaryotic common ancestor.

developmental biology↗

bioRxiv2023

Reduced S-acylation of SQSTM1/p62 in Huntington disease is associated with impaired autophagy

Disruption of macroautophagy/autophagy has emerged as a common feature in many neurodegenerative diseases. Autophagy is a membrane-dependent pathway that requires many key regulators to quickly localize on and off membranes during induction promoting membrane fusion. Previously, our bioinformatic approaches have shown that autophagy and Huntington disease (HD) are enriched in S-acylated proteins. S-acylation involves the reversible addition of long chain fatty acids to promote membrane binding. Herein, we show that inhibition of S-acylation regulates the abundance of several key regulators of autophagy and leads to a partial block of autophagic flux. We show that the autophagy receptor SQSTM1/p62 (sequestosome 1) is S-acylated and directed to the lysosome. Importantly, we see that SQSTM1 S-acylation is significantly reduced in HD patient and mouse model brains, thus providing a novel mechanism for the generation of empty autophagosomes previously seen in HD models and patient cells.

neuroscience↗

bioRxiv2023

m6a methylation orchestrates IMP1 regulation of microtubules during human neuronal differentiation

Neuronal differentiation requires building a complex intracellular architecture, and therefore the coordinated regulation of defined sets of genes. RNA-binding proteins (RBPs) play a key role in this regulation. However, while their action on individual mRNAs has been explored in depth, the mechanisms used to coordinate expression of the gene programs shaping neuronal morphology are poorly understood. To address this, we analysed how the paradigmatic RBP IMP1 (IGF2BP1), an essential developmental factor, selects and regulates its RNA targets during the differentiation of human neurons. We performed a combination of system-wide and molecular analyses, revealing that IMP1 developmentally transitions to and directly regulates the expression of mRNAs encoding essential regulators of the microtubule network, a key component of neuronal morphology. Furthermore, we showed that m6A methylation drives the selection of specific IMP1 mRNA targets and their protein expression during the developmental transition from neural precursors to neurons, providing a molecular principle for the onset of target selectivity.

molecular biology↗

bioRxiv2020

CEDAR, an online resource for the reporting and exploration of complexome profiling data

Complexome profiling is an emerging omics approach that systematically interrogates the composition of protein complexes (the complexome) of a sample, by combining biochemical separation of native protein complexes with mass-spectrometry based quantitation proteomics. The resulting fractionation profiles hold comprehensive information on the abundance and composition of the complexome, and have a high potential for reuse by experimental and computational researchers. However, the lack of a central resource that provides access to these data, reported with adequate descriptions and an analysis tool, has limited their reuse. Therefore, we established the ComplexomE profiling DAta Resource (CEDAR, www3.cmbi.umcn.nl/cedar/), an openly accessible database for depositing and exploring mass spectrometry data from complexome profiling studies. Compatibility and reusability of the data is ensured by a standardized data and reporting format containing the "minimum information required for a complexome profiling experiment" (MIACE). The data can be accessed through a user-friendly web interface, as well as programmatically using the REST API portal. Additionally, all complexome profiles available on CEDAR can be inspected directly on the website with the profile viewer tool that allows the detection of correlated profiles and inference of potential complexes. In conclusion, CEDAR is a unique, growing and invaluable resource for the study of protein complex composition and dynamics across biological systems.

bioinformatics↗

bioRxiv2020

A commercial antibody to the human condensin II subunit NCAPH2 cross-reacts with a SWI/SNF complex component

Condensin complexes compact and disentangle chromosomes in preparation for cell division. Commercially available antibodies raised against condensin subunits have been widely used to characterise their cellular interactome. Here we have assessed the specificity of a polyclonal antibody (Bethyl A302-276A) that is commonly used as a probe for NCAPH2, the kleisin subunit of condensin II, in mammalian cells. We find that, in addition to its intended target, this antibody cross-reacts with one or more components of the SWI/SNF family of chromatin remodelling complexes in an NCAPH2-independent manner. This cross-reactivity with an abundant chromatin-associated factor is likely to affect the interpretation of protein and chromatin immunoprecipitation experiments that make use of this antibody probe.

cell biology↗

bioRxiv2020

UFMylation regulates translational homeostasis and cell cycle progression

UFMylation, the posttranslational modification of proteins with ubiquitin fold modifier 1 (UFM1) is essential for metazoan life and is associated with multiple human diseases. Although UFMylation has been linked to endoplasmic reticulum (ER) stress, its biological functions and relevant cellular targets beyond the ER are obscure. Here, we show that UFMylation directly controls translation and cell division in a manner otherwise known for cellular homeostasis-sensing pathways such as mTOR. By combining cell cycle analyses, mass spectrometry and ribosome profiling we demonstrate that UFMylation is required for eIF4F translation initiation complex assembly and recruitment of the ribosome. Interference with UFMylation shuts down global translation, which is sensed by cyclin D1 and halts the cell cycle independently of integrated stress response signalling. Our findings establish UFMylation as a key regulator of translation and uncover a pathway that couples translational homeostasis to cell cycle progression via a ubiquitin-like modification.

cell biology↗