Biology subjects

Deluz, C.

Publications and source records attributed to Deluz, C..

7 recordsLinked to original sources

bioRxiv2026

The role of charge, hydrophobicity, and cooperativity in target search of SOX2 and ESRRB

Transcription factors (TFs) locate and bind specific DNA sequences within a crowded nuclear environment, yet how their biophysical properties and interactions influence their search remains unclear. Here, we modulate hydrophobicity and charge of the pluripotency TFs SOX2 and ESRRB, and combine single-molecule imaging with genomic analyses to dissect their target search dynamics. We show that increased hydrophobicity impairs specific binding while promoting confined intranuclear interactions, whereas additional negative charges decrease sampling of weak binding sites. While SOX2 retains effective target site recognition despite decreased search efficiency, impairment of ESRRB search results in a global loss of genome occupancy and redirection to SOX2-bound regions, indicating a strong reliance of ESRRB on TF-TF interactions for locating its binding sites. Single molecule imaging analysis of ESRRB search upon SOX2 depletion demonstrated that SOX2 reduces ESRRB search time by restricting its nuclear diffusion and facilitating stable DNA binding. Together, our findings highlight how TF biophysical features and cooperativity jointly shape the efficiency and specificity of target search in the nucleus.

molecular biology↗

bioRxiv2025

Endogenous variability in transcription factor concentrations shapes their genome-wide occupancy

The control of transcription factor (TF) concentrations is crucial for the precise regulation of gene expression and cell fate decisions during development. Yet, TF concentrations can display substantial temporal fluctuations and intercellular variations. How TF levels quantitatively shape genome-wide occupancy patterns remains largely unexplored. Here, we systematically investigate how physiological fluctuations in the concentrations of the pluripotency TFs OCT4, SOX2, and NANOG impact their genomic binding profiles in mouse embryonic stem cells. We uncover distinct concentration-dependent binding behaviors for each TF. NANOG occupancy increased monotonously with its concentration, even though a common set of regions made accessible by OCT4 and SOX2 are highly and uniformly bound at all NANOG concentrations. In contrast, SOX2 occupancy does not increase with its concentrations, while OCT4 displayed an intermediate behavior. Our results challenge the notion that TF binding follows simple mass-action dynamics and reveal a core set of pluripotency regions that are bound by all three TFs at all TF concentrations, revealing how pluripotency can be maintained despite marked fluctuations in core pluripotency TFs.

genomics↗

bioRxiv2024

Coordination of protein synthesis and decay in mammalian cells

The maintenance of cellular homeostasis requires tight regulation of proteome concentration and composition. To achieve this, protein production and elimination must be robustly coordinated. However, the mechanistic basis of this coordination remains unclear. Here, we address this question using quantitative live cell imaging, computational modeling, transcriptomics, and proteomics approaches. We found that protein decay rates systematically adapt to global alterations of protein synthesis rates. This adaptation is driven by a core passive mechanism supplemented by facultative changes in mTOR signaling. Passive adaptation hinges on changes in the production rate of the machinery governing protein decay and allows partial maintenance of the cellular proteome. Sustained changes in mTOR signaling provide an additional layer of adaptation unique to naive pluripotent stem cells, allowing near-perfect maintenance of proteome composition. Our work unravels the mechanisms protecting the integrity of mammalian proteomes upon variations in protein synthesis rates.

cell biology↗

bioRxiv2024

Mechanistic basis of gene regulation by SRCAP and H2A.Z

Discriminating regulatory functions of chromatin composition from those of chromatin-modifying complexes is a central problem in gene regulation. This question remains unexplored in the context of histone variants and their dedicated chromatin remodelers. Here we dissect the distinct and cell cycle-dependent functions of Snf2 Related CREBBP Activator Protein (SRCAP) and H2A.Z in gene regulation of pluripotent stem cells. We uncover dynamic changes of H2A.Z occupancy and continuous requirement of SRCAP over the cell cycle. We discover that SRCAP exhibits essential H2A.Z-independent functions in inhibiting DNA binding of dozens of pioneer transcription factors at enhancers by steric hindrance. In contrast, H2A.Z acts mainly as a transcriptional repressor gatekeeping the expression of lineage-specific genes. Our study establishes the catalytic-independent role of a chromatin remodeler in broadly regulating transcription factor binding, and demonstrates how a chromatin remodeler-histone variant pair orchestrates transcription to maintain self-renewal and plasticity of pluripotent stem cells.

molecular biology↗

bioRxiv2019

Dynamic regulation of chromatin accessibility by pluripotency transcription factors across the cell cycle

The pioneer activity of transcription factors allows for opening of inaccessible regulatory elements and has been extensively studied in the context of cellular differentiation and reprogramming. In contrast, the function of pioneer activity in self-renewing cell divisions and across the cell cycle is poorly understood. Here we assessed the interplay between OCT4 and SOX2 in controlling chromatin accessibility of mouse embryonic stem cells. We found that OCT4 and SOX2 operate in a largely independent manner even at co-occupied sites, and that their cooperative binding is mostly mediated indirectly through regulation of chromatin accessibility. Controlled protein degradation strategies revealed that the uninterrupted presence of OCT4 is required for post-mitotic re-establishment and interphase maintenance of chromatin accessibility, and that highly OCT4-bound enhancers are particularly vulnerable to transient loss of OCT4 expression. Our study sheds light on the constant pioneer activity required to maintain the dynamic pluripotency regulatory landscape in an accessible state.

genomics↗

bioRxiv2018

Mitotic chromosome binding predicts transcription factor properties in interphase

Mammalian transcription factors (TFs) differ broadly in their nuclear mobility and sequence-specific/non-specific DNA binding affinity. How these properties affect the ability of TFs to occupy their specific binding sites in the genome and modify the epigenetic landscape is unclear. Here we combined live cell quantitative measurements of mitotic chromosome binding (MCB) of 502 TFs, measurements of TF mobility by fluorescence recovery after photobleaching, single molecule imaging of DNA binding in live cells, and genome-wide mapping of TF binding and chromatin accessibility. MCB scaled with interphase properties such as association with DNA-rich compartments, mobility, as well as large differences in genome-wide specific site occupancy that correlated with TF impact on chromatin accessibility. As MCB is largely mediated by electrostatic, non-specific TF-DNA interactions, our data suggests that non-specific DNA binding of TFs enhances their search for specific sites and thereby their impact on the accessible chromatin landscape.

genomics↗

bioRxiv2018

Endogenous fluctuations of OCT4 and SOX2 bias pluripotent cell fate decisions

SOX2 and OCT4 are pioneer transcription factors playing a key role in embryonic stem (ES) cell self-renewal and differentiation. However, how temporal fluctuations in their expression levels bias lineage commitment is unknown. Here we generated knock-in reporter fusion ES cell lines allowing to monitor endogenous SOX2 and OCT4 protein fluctuations in living cells and to determine their impact on mesendodermal and neuroectodermal commitment. We found that small differences in SOX2 and OCT4 levels impact cell fate commitment in G1 but not in S phase. Elevated SOX2 levels modestly increased neuroectodermal commitment and decreased mesendodermal commitment upon directed differentiation. In contrast, elevated OCT4 levels strongly biased ES cell towards both neuroectodermal and mesendodermal fates. Using ATAC-seq on ES cells gated for different endogenous SOX2 and OCT4 levels, we found that high OCT4 levels increased chromatin accessibility at differentiation-associated enhancers. This suggests that small endogenous fluctuations of pioneer transcription factors can bias cell fate decisions by concentration-dependent priming of differentiation-associated enhancers.

developmental biology↗