Biology subjects

Erdelyi, M.

Publications and source records attributed to Erdelyi, M..

13 recordsLinked to original sources

bioRxiv2026

The multifunctional scaffold protein Small ovary couples piRNA-guided transposon recognition to nuclear RNA decay and heterochromatin formation

The piRNA pathway maintains genome integrity by silencing transposons cotranscriptionally in the nucleus through recognition of nascent transposon RNAs and recruitment of endogenous transcriptional and chromatin-level repressive mechanisms to transposon loci. However, the molecular link between the SFiNX complex, which recognizes nascent transposon RNA, and downstream effector complexes has remained elusive. Here, we demonstrate that the Small ovary (Sov) protein mediates this connection. By mapping the functional activities of its structural elements, we reveal that Sov contributes to transposon silencing through two distinct molecular mechanisms. First, Sov specifically directs nascent transposon transcripts toward nuclear RNA exosome-mediated degradation by physically interacting with the RNA decay factor TEsup1. Second, Sov directly binds the heterochromatin protein HP1a via multiple conserved motifs and undergoes phase separation, facilitating heterochromatin formation and genome-wide gene repression. Genetic analyzes of sov mutants reveal that these functions are separable: RNA-mediated transcriptional silencing is essential for piRNA pathway activity, while phase separation-dependent heterochromatin regulation is critical for stable transposon repression. We propose that Sov acts as a molecular scaffold in piRNA-guided transposon silencing, integrating transposon recognition with cotranscriptional RNA decay and chromatin-based regulatory pathways.

molecular biology↗

bioRxiv2026

An Atlas of Short Linear Motif-Mediated Human Protein-Protein Interactions

Short linear motifs (SLiMs) within intrinsically disordered protein regions mediate transient interactions crucial for cell physiology1. However, the global interaction landscape of human SLiMs remains largely uncharted. Here we present the Atlas of SLiM-mediated Human protein-protein Interactions (ASHI), which maps more than 20,000 interactions by screening over 800 human protein domains against a library of one million peptides tiling the human disordered proteome. ASHI expands the SLiM interactome, uncovers novel binding modes for known peptide-binding domains, and reveals unexpected peptide-binding activities in enzymes, chaperones, RNA-binding proteins, and modification-reader domains. Furthermore, intrinsically disordered regions emerge as densely encoded interaction platforms where interaction specificity is governed by diverse mechanisms, including key motif determinants, flanking residues, competition, and multivalency. These data provide an unprecedented foundation for modeling dynamic interaction networks, interpreting disease-associated variants, and decoding the dark proteome.

biochemistry↗

bioRxiv2026

Flightless I and LRRFIP work together to regulate lateral growth of the sarcomeres in Drosophila

Myofibrils are structurally highly conserved elements of the cardiac and striated muscles. The striking commonalities in their basic organization principles emerge during myofibrillogenesis when the initially formed premyofibrils grow in length and width to attain their final dimensions, characteristic of each muscle type. Although the molecular composition of the myofibrils is well known, the mechanisms governing their growth remain poorly understood, particularly those driving peripheral thickening. Here, we show that two cardiac disease associated proteins, Flightless I and LRRFIP, are required for lateral integration of the myofilaments that is essential for circumferential myofibril growth in the Drosophila flight muscle. Genetic and biochemical analysis reveal that these proteins form multimeric complexes enriched at the barbed end of the actin filaments. Furthermore, we found that the Flightless I/LRRFIP complex acts in a formin dependent manner. Together, our findings demonstrate that Flightless I and LRRFIP cooperate to promote the spatially controlled integration of peripheral actin filaments at the Z-disc, uncovering a key step in myofibril maturation.

cell biology↗

bioRxiv2026

Recognizing dUTPase as a mitotic factor essential for early embryonic development

dUTPase is universally regarded as a metabolic sanitizing enzyme that protects genomes by preventing the incorporation of uracil into DNA. Despite its essentiality across eukaryotes, no function beyond nucleotide sanitization has been demonstrated. Here, we uncover a conserved, non-canonical role for dUTPase as a regulator of mitosis. Using Drosophila and mouse models, we demonstrate that dUTPase loss causes early embryonic lethality characterized by severe mitotic failure that, cannot be rescued by disabling uracil-DNA repair, uncoupling dUTPase essentiality from DNA repair pathways. Mechanistically, dUTPase dynamically associates with the mitotic spindle and centrosomes, and its depletion induces centrosome amplification and chromosome segregation defects. Beyond cell division, dUTPase dosage bidirectionally controls cell migration, linking its mitotic function to cellular behaviors relevant for metastasis. Together, our findings redefine dUTPase as a moonlighting mitotic factor that coordinates centrosome integrity and spindle dynamics, expanding its known repertoire beyond nucleotide metabolism. HighlightsdUTPase deficiency leads to mitotic defects during early embryonic development in both Drosophila and mouse models dUTPase shows dynamic spatiotemporal localization associated with microtubules through mitosis dUTPase is essential for the normal number and intracellular localization of centrosomes dUTPase deficiency counteracts while its overexpression enhances cell migration

molecular biology↗

bioRxiv2025

Endothelial tight junctions and cell-matrix adhesions reciprocally control blood-brain barrier integrity

Brain endothelial cells (ECs) rely on mechanical cues to provide a physical barrier that protects the brain. Yet how ECs integrate forces to establish and maintain the blood-brain barrier (BBB) remains poorly understood. Here, we show that the two main endothelial force-bearing systems, tight junctions and cell-matrix adhesions, reciprocally control BBB integrity. Using a combination of super-resolution imaging and biophysical techniques, we reveal increasing mechanical loads on cell-cell junctions vs. cell-matrix adhesions in human stem cell-derived ECs during BBB maturation. This force redistribution is enabled by cytoskeletal remodeling, a compacted pattern of the tight junction protein claudin-5, and the emergence of specialised perinuclear cell-matrix adhesions. Mechanistically, we find an inverse relationship between claudin-5 levels and the expression of key cell-matrix adhesion proteins zyxin and vinculin in vitro and in mice. Finally, we demonstrate that this mechanobiological signature associated with BBB maturation is reversed upon BBB dysfunction after seizures in mice and in human patients with temporal lobe epilepsy. Collectively, our findings establish a novel interplay between mechanoresponsive elements in brain ECs, with implications for BBB stabilisation therapy in epilepsy.

neuroscience↗

bioRxiv2025

Regulation of input excitability in human and mouse parvalbumin interneurons by Kir potassium channels

Compared to rodents, inhibitory interneurons in the human neocortex exhibit high input excitability because of reduced passive ion leakage across their extracellular membrane. However, the regulation of intrinsic excitability by voltage-gated ion channels activated over a wide range of membrane potentials in human interneurons remains poorly understood. We performed whole-cell patch-clamp microelectrode recordings in mouse and human neocortical slices obtained from surgically resected non-pathological brain tissue finding that Kir channels control the electrical resistance of parvalbumin (Pvalb) neurons in an identical manner in the human and mouse. Molecular analyses revealed predominantly Kir3.1 and Kir3.2 channels in Pvalb neurons in both species. Using whole-cell recordings from synaptically connected neuron pairs and a computational model, we demonstrated that physiological Kir activation inhibits human Pvalb interneurons during postsynaptic potentials evoked by presynaptic neurogliaform cells. The similarity of Kir-mediated inhibition across species suggests that it is an archetypal property of Pvalb neurons.

neuroscience↗

bioRxiv2025

A myofilament lattice model of Drosophila flight muscle sarcomeres based on multiscale morphometric analysis during development

The indirect flight muscle is a widely used model for studying sarcomere structure and muscle development due to its extremely regular architecture. Nevertheless, precise measurement of the basic sarcomeric parameters remains a challenge even in this greatly ordered tissue. In this study, we identified several factors affecting measurement reliability and developed a software tool for precise, high-throughput measurement of sarcomere length and myofibril width. The accuracy of this new tool was validated against simulated images and blinded manual measurements. To extend the scope of this morphometric analysis to the sub-sarcomeric scale, we used electron and super-resolution microscopy to quantify myofilament number and filament length during myofibrillogenesis. These results provided novel insights into the dynamics of sarcomere growth, and enabled us to construct a refined model of sarcomere growth reaching to the level of individual myofilaments and providing a spatial framework for interpreting molecular localization data. These findings enhance our understanding of sarcomere assembly and offer a foundation for future studies of muscle development and function. SUMMARY STATEMENTThis study identifies factors influencing sarcomere size measurements, introduces a validated tool for precise analysis, and presents a comprehensive model of Drosophila flight muscle sarcomere growth during muscle development.

developmental biology↗

bioRxiv2024

Mild hyperthermia-induced thermogenesis in the endoplasmic reticulum defines stress response mechanisms

Previous studies reported that a mild, non-protein denaturing, fever-like temperature increase induced the unfolded protein response (UPR) in mammalian cells. Our dSTORM super-resolution microscopy experiments revealed that the master regulator of the UPR, the IRE1 (inositol-requiring enzyme 1) protein is clustered as a result of UPR activation in a human osteosarcoma cell line (U2OS) upon mild heat stress. Using ER thermo yellow, a temperature-sensitive fluorescent probe targeted to the endoplasmic reticulum (ER), we detected significant intracellular thermogenesis in mouse embryonic fibroblast (MEF) cells. Temperatures reached at least 8{degrees}C higher than the external environment (40{degrees}C), resulting in exceptionally high ER temperatures similar to those previously described for mitochondria. Mild heat-induced thermogenesis in the ER of MEF cells was likely due to the uncoupling of the Ca2+/ATPase (SERCA) pump. The high ER temperatures initiated a pronounced cytosolic heat shock response in MEF cells, which was significantly lower in U2OS cells in which both the ER thermogenesis and SERCA pump uncoupling were absent. Our results suggest that, depending on intrinsic cellular properties, mild hyperthemia-induced intracellular thermogenesis defines the cellular response mechanism, and determines the outcome of hyperthermic stress.

cell biology↗

bioRxiv2022

Phase separated ribosome nascent chain complexes paused in translation are capable to continue expression of proteins playing role in genotoxic stress response upon DNA damage

EDTA- and RNase-resistant ribonucleoprotein complexes of arrested ribosomes with protruding nascent polypeptide chains have recently been described in yeast and human cells. These complexes have been termed assemblysomes, a type of soluble condensates distinct from other known granules. Here, we use bioinformatics to identify additional proteins that likely form assemblysomes during translation. We characterize soluble condensates of the DNA helicase Sgs1, one such identified protein and a key player in the repair of DNA double-strand breaks in yeast. We show that paused ribosome-associated nascent chains of Sgs1 in condensates are able to resume translation upon UV irradiation, consistent with the return of mRNA to the ribosome pool. By extending our studies to human cell lines, we found that EDTA-resistant pellets of ribosomes from the human prostate cancer cell line DU145 are sensitive to treatment with 1,6-hexanediol, which is known to dissolve liquid-liquid phase-separated condensates. In addition, transmission electron microscopy shows that 1,6-hexanediol dissolves ring ribosomal structures from the cytoplasm of radioresistant A549 cells while making the cells more sensitive to X-rays. These results suggest that the stress response is based on a conserved mechanism involving the regulated return of phase-separated paused ribosome-nascent chain complexes to translating ribosomes.

molecular biology↗

bioRxiv2021

Oxoglutarate dehydrogenase coordinates myofibril growth by maintaining amino acid homeostasis

Myofibrils are long intracellular cables specific to muscles, composed mainly of actin and myosin filaments. The actin and myosin filaments are organized into repeated units called sarcomeres, which form the myofibril cables. Muscle contraction is achieved by the simultaneous shortening of sarcomeres and for a highly coordinated contraction to occur all sarcomeres should have the same size. Muscles have evolved a variety of ways to ensure sarcomere homogeneity, one example being the controlled oligomerization of Zasp proteins that sets the diameter of the myofibril. To understand how Zasp proteins effect myofibril growth, we looked for Zasp-binding proteins at the Z-disc. We found that the E1 subunit of the oxoglutarate dehydrogenase complex is recruited to the Z-disc by Zasp52 and is required to sustain myofibril growth. By making specific mutants, we show that its enzymatic activity is important for myofibril growth, and that the other two subunits of the complex are also required for myofibril formation. Using super resolution microscopy, we revealed the overall organization of the complex at the Z-disc. Then, using metabolomic analysis, we uncovered an amino acid balance defect affecting protein synthesis, that we also confirmed by genetic tools. In summary, we show that Zasp controls the local amino acid pool responsible for myofibril growth by recruiting the OGDH complex to the Z-disc.

cell biology↗

bioRxiv2019

Quantification of DNA damage induced γH2AX focus formation via super-resolution dSTORM localization microscopy

In eukaryotic cells, each process, in which DNA is involved, should take place in the context of chromatin structure. DNA double-strand breaks (DSBs) are one of the most deleterious damages often leading to chromosomal rearrangement. In response to environmental stresses, cells have developed repair mechanisms to eliminate the DSBs. Upon DSB induction, several factors play roles in chromatin relaxation by catalysing the appropriate histone posttranslational modification (PTM) steps, therefore promoting the access of the repair factors to the DSBs. Among these PTMs, the phosphorylation of the histone variant H2AX at its Ser139 residue (also known as {gamma}H2AX) could be observed at the break sites. The structure of {gamma}H2AX focus has to be organized during the repair as it contributes to accessibility of specific repair proteins to the damaged site. Our aim was to develop a quantitative approach to analyse the morphology of individual repair foci by super-resolution dSTORM microscopy to gain insight into genome organization in DNA repair. We have established a specific dSTORM measurement process by developing a new analytical algorithm for gaining quantitative information about chromatin morphology and repair foci topology at individual {gamma}H2AX enriched repair focus. By this method we quantified unique repair foci to show the average distribution of {gamma}H2AX clusters. By monitoring {gamma}H2AX signal, we could reach 20 nm spatial resolution and resolve a single DNA damage spot, which allow us to identify different chromatin sub-clusters around the break site. Additionally, based on our new analysis method, we were able to show the number of nucleosomes in each sub-cluster that could allow us to define the possible chromatin structure and the nucleosome density around the break sites. This method is the first demonstration of a single-cell based quantitative measurement of a discrete repair focus, which could provide new opportunities to categorize spatial organization of dot patterns by parametric determination of topological similarity.

cell biology↗

bioRxiv2019

The SUMO ligase Su(var)2-10 controls eu- and heterochromatic gene expression via establishment of H3K9 trimethylation and negative feedback regulation

Chromatin is critical for genome compaction and gene expression. On a coarse scale, the genome is divided into euchromatin, which harbors the majority of genes and is enriched in active chromatin marks, and heterochromatin, which is gene-poor but repeat-rich. The conserved molecular hallmark of heterochromatin is the H3K9me3 modification, which is associated with gene silencing. We found that in Drosophila deposition of most of the H3K9me3 mark depends on SUMO and the SUMO-ligase Su(var)2-10, which recruits the histone methyltransferase complex SetDB1/Wde. In addition to repressing repeats, H3K9me3 also influences expression of both hetero- and euchromatic host genes. High H3K9me3 levels in heterochromatin are required to suppress spurious non-canonical transcription and ensure proper gene expression. In euchromatin, a set of conserved genes is repressed by Su(var)2-10/SetDB1-induced H3K9 trimethylation ensuring tissue-specific gene expression. Several components of heterochromatin are themselves repressed by this pathway providing a negative feedback mechanism to ensure chromatin homeostasis. Highlights- Proper expression of host genes residing in heterochromatin requires Su(var)2-10-dependent installation of the H3K9me3 mark to suppress spurious non-canonical transcription. - A set of euchromatic host genes is repressed by transposon-independent installation of H3K9me3 in a process that depends on Su(var)2-10 and SUMO. - Installation of H3K9me3 via Su(var)2-10 ensures tissue-specific gene expression. - H3K9me3-dependent silencing of genes encoding proteins involved in heterochromatin formation provides negative feedback regulation to maintain heterochromatin homeostasis.

molecular biology↗

bioRxiv2018

Drosophila small ovary gene ensures germline stem cell maintenance and differentiation by silencing transposons and organising heterochromatin

Self-renewal and differentiation of stem cells is one of the fundamental biological phenomena relying on proper chromatin organisation. In our study, we describe a novel chromatin regulator encoded by the Drosophila small ovary (sov) gene. We demonstrate that sov is required in both the germline stem cells (GSCs) and the surrounding somatic niche cells to ensure GSC survival and differentiation. Sov maintains niche integrity and function by repressing transposon mobility, not only in the germline, but also in the soma. Protein interactome analysis of Sov revealed a physical interaction between Sov and HP1a. In the germ cell nuclei, Sov co-localises with HP1a, suggesting that Sov affects transposon repression as a component of the heterochromatin. In a position effect variegation assay, we found a dominant genetic interaction between sov and HP1a, indicating their functional cooperation in promoting the spread of heterochromatin. An in vivo tethering assay and FRAP analysis revealed that Sov enhances heterochromatin formation by supporting the recruitment of HP1a to the chromatin. We propose a model in which sov maintains GSC niche integrity by regulating piRNA-mediated transposon silencing as a heterochromatin regulator.\n\nSummary statementSmall ovary maintains the integrity of the stem cell niche by regulating piRNA-mediated transposon silencing acting as a key component of the heterochromatin.

developmental biology↗