Biology subjects

Graus, M. S.

Publications and source records attributed to Graus, M. S..

5 recordsLinked to original sources

bioRxiv2025

Oncogenic virus hijacks SOX18 pioneer function to enhance viral persistence

Kaposis sarcoma herpesvirus (KSHV) establishes lifelong oncogenic infection in lymphatic endothelial cells (LECs) by ensuring episomal maintenance of its genome via the viral protein LANA. Efficient viral genome maintenance typically involves host DNA replication and episome tethering, but the extent of cell-type-specific regulation remains unclear. Here, we identify that KSHV hijacks the pioneering function of the endothelial-specific transcription factor SOX18 to facilitate persistence of viral episomes. Upon infection, LANA co-opts SOX18 to recruit the SWI/SNF chromatin-remodeling complex via its ATPase subunit BRG1, enhancing chromatin accessibility and enabling efficient viral genome persistence. Disruption of SOX18 or BRG1--genetically or pharmacologically--leads to reduced episome load and attenuated hallmarks of virus infection. This work highlights how viruses can harness lineage-specific transcriptional regulators to establish persistent nuclear retention of their episome into the host genome.

molecular biology↗

bioRxiv2025

Inhibiting SOX18 with propranolol restores vascular integrity in NR2F2-driven malformations

Translating genomic discoveries into therapies for rare genetic disorders remains a significant challenge, particularly for variants of unknown significance (VUS) where molecular mechanisms are unclear. This is particularly relevant in vascular malformations, where venous differentiation remains poorly understood, and the role of transcription factors in specifying venous identity is only beginning to be elucidated. Here, we combine live-cell single-molecule imaging with genomics-based approaches to uncover a biophysical mechanism of transcription factor antagonism that underpins venous identity. We show that SOX18 and NR2F2 antagonistically co-regulate venous differentiation through dynamic feedback between their nuclear populations. This interaction is disrupted in vascular malformation syndrome caused by a de novo heterozygous NR2F2 mutation, presenting with aberrant vascular integrity and bleeding. Treatment with an FDA-approved drug--known to inhibit SOX18--led to marked clinical improvement in the proband. To dissect the molecular mechanism underlying this mutation and the drug response, we used human embryonic stem cells (hESCs) engineered to carry the probands NR2F2 variant. These cells exhibited impaired hESC to venous differentiation with no effect on artery EC differentiation. In silico modelling and live-cell molecular imaging revealed that the NR2F2 variant is hyper-mobile, fails to form homodimers, and cannot recruit SOX18, thereby disrupting a critical transcriptional antagonism that underpins venous endothelial identity. We demonstrate that targeted pharmacological inhibition of SOX18 restores this regulatory balance in hESC-derived venous endothelial cells, rescuing both gene expression and NR2F2 binding dynamics at the single-molecule level. Together, this study uncovers a biophysical mechanism of transcription factor antagonism that governs venous differentiation and offers a framework for developing targeted therapies for rare vascular malformations.

developmental biology↗

bioRxiv2024

Anti-phase clustering of regulatory factors shapes gene bursting

Stem cell self-renewal relies on finely tuned transcriptional oscillations of pluripotency genes, yet the sequence by which transcription factors (TFs) govern "on" and "off" states remains unclear. Here, we integrate trimodal single-molecule imaging - SOX2 mobility, Nanog locus diffusion, and real-time Nanog mRNA synthesis using the STREAMING-tag reporter - to visualise endogenous regulatory dynamics in living cells. We identify two SOX2 binding modes linked to transcriptional priming and termination and show coordinated temporal activity of SOX2, OCT4, BRD4, and MED22 at the Nanog locus. Live-cell and fixed-cell measurements reveal that local RNA fluctuations modulate SOX2 visiting-frequency rates. During the active elongation, high nascent enhancer and mRNA levels transiently sequester SOX2 through non-specific interactions, reducing its effective repetitive rebinding and limiting interference with elongating polymerase. After transcript release, declining RNA density permits SOX2 re-engagement, with high-visiting frequency with longer residency and increased locus mobility. These dynamics reveal RNA-dependent feedback that alternately buffers and primes transcriptional re-initiation.

molecular biology↗

bioRxiv2018

Single molecule localization microscopy with autonomous feedback loops for ultrahigh precision

Single-molecule localization microscopy (SMLM) promises to provide truly molecular scale images of biological specimens1-5. However, mechanical instabilities in the instrument, readout errors and sample drift constitute significant challenges and severely limit both the useable data acquisition length and the localization accuracy of single molecule emitters6. Here, we developed an actively stabilized total internal fluorescence (TIRF) microscope that performs 3D real-time drift corrections and achieves a stability of [≤]1 nm. Self-alignment of the emission light path and corrections of readout errors of the camera automate channel alignment and ensure localization precisions of 1-4 nm in DNA origami structures and cells for different labels. We used Feedback SMLM to measure the separation distance of signaling receptors and phosphatases in T cells. Thus, an improved SMLM enables direct distance measurements between molecules in intact cells on the scale between 1-20 nm, potentially replacing Forster resonance energy transfer (FRET) to quantify molecular interactions7. In summary, by overcoming the major bottlenecks in SMLM imaging, it is possible to generate molecular images with nanometer accuracy and conduct distance measurements on the biological relevant length scales.

biophysics↗

bioRxiv2017

Mannan molecular sub-structures control nanoscale glucan exposure in Candida

N-linked mannans (N-mannans) in the cell wall of Candida albicans are thought to mask {beta}-(1,3)-glucan from recognition by Dectin-1, contributing to innate immune evasion. Lateral cell wall exposures of glucan on Candida albicans are predominantly single receptor-ligand interaction sites and are restricted to nanoscale geometries. Candida species exhibit a range of basal glucan exposures and their mannans also vary in size and complexity at the molecular level. We used super resolution fluorescence imaging and a series of protein mannosylation mutants in C. albicans and C. glabrata to investigate the role of specific N-mannan features in regulating the nanoscale geometry of glucan exposure. Decreasing acid labile mannan abundance and -(1,6)-mannan backbone length correlated most strongly with increased density and nanoscopic size of glucan exposures in C. albicans and C. glabrata, respectively. Additionally, a C. albicans clinical isolate with high glucan exposure produced similarly perturbed N-mannan structures and exhibited similar changes to nanoscopic glucan exposure geometry. We conclude that acid labile N-mannan controls glucan exposure geometry at the nanoscale. Furthermore, variations in glucan nanoexposure characteristics are clinically relevant and are likely to impact the nature of the pathogenic surface presented to innate immunocytes at dimensions relevant to receptor engagement, aggregation and signaling.

microbiology↗