Biology subjects

Campalans, A.

Publications and source records attributed to Campalans, A..

8 recordsLinked to original sources

bioRxiv2026

Direct effects on gene transcription revealed by global and CRISPR-targeted oxidative DNA damage

Oxidative stress induces rapid expression changes of specific genes. However, whether these changes are due to direct and local DNA oxidation and whether they depend on the repair machinery is still debated. Here, we show by total RNA-Seq that upon oxidative stress, many genes are either rapidly repressed or activated. The early transcriptional response also includes the activation of many read-through RNAs. Importantly, degradation of the endogenous OGG1 DNA glycosylase showed that the early repression of these genes partially depends on OGG1, therefore demonstrating that these genome expression changes are due to the processing of oxidized DNA. We further demonstrate by ChIPseq against total or S5-phosphorylated RNA polymerase II that transcriptional regulation by oxidative stress involves changes in the recruitment of RNA polymerase II to transcription start sites. Finally, through the use of a chemoptogenetic system allowing the targeting of ROS to chosen genomic loci, we were able to reproduce repression of some genes through the local induction of oxidative DNA damage at their promoters, demonstrating that local DNA oxidation directly affects transcription of genes. Altogether, our results show that local oxidative DNA damage leads to alterations in the activity of specific promoters by a mechanism dependent on repair processes.

genomics↗

bioRxiv2025

A coordinated haptic mechanism ensures efficient DNA sampling by the 8-oxoguanine glycosylase OGG1.

7,8-Dihydro-8-oxoguanine (8-oxoG) is the most frequent base modification occurring upon oxidative stress. This highly mutagenic lesion is specifically recognized and excised by the DNA glycosylase OGG1 when paired with cytosine, initiating the base excision repair pathway. Since 8-oxoG neither significantly impacts the structure of the double helix nor blocks transcription and replication processes, its detection requires a careful inspection of each base pair by OGG1. By monitoring this lesion search process both in vitro and in living cells, we demonstrate that it involves a tight coordination between several conserved amino acids encircling the DNA helix. More specifically, we show that the N149-151 motif, on the target strand, as well as residues R154 and R204, on the opposite strand, both regulate OGG1 engagement on the DNA to ensure fast Y203-mediated base unstacking, a prerequisite for efficient 8-oxoG detection. These findings highlight the early mechanisms that enable OGG1 to maintain rapid sampling kinetics while preserving high specificity for 8-oxoG in the context of the complex architecture displayed by the DNA within the cell nucleus.

genetics↗

bioRxiv2025

The uptake of metallic nanoparticles in breast cancer cell lines is modulated by the HA-CD44 axis.

Radiation enhancement is a promising anti-cancer approach based on a local radiation dose increase due to the presence of metallic nanoparticles (NPs) within cancer cells. Depending on their composition, size and cellular properties, NPs can follow multiple cellular pathways and entry routes. We observed that gold, platinum and TiO2 NPs are internalized at higher levels in mesenchymal cells compared to epithelial cells in breast cancer models. A global survey of gene expression between epithelial and mesenchymal cells exposed to 4 different NP types revealed an involvement of membrane structure, and further experiments confirmed that the hyaluronic acid (HA) and its receptor CD44 are mediators of metallic NP uptake into cells. We extended our results to a larger panel of breast cancer cell lines and again showed a preferential uptake of all NPs tested in mesenchymal cells and relying on the HA/CD44 axis. These data provide considerations for the design of NP-based therapies targeting mesenchymal cancer cells, which are often resistant to treatment and correlate with poor prognosis and tumor recurrence.

cancer biology↗

bioRxiv2024

G-quadruplex ligand RHPS4 compromises cellular radio-resistance by blocking the increase in mitochondrial mass and activity induced by ionising irradiation.

A major challenge in radiotherapy is to enhance tumor cell sensitivity to radiation while minimizing damage to healthy tissues. Ionising radiation (IR) induces mitochondrial DNA (mtDNA) alterations that can impair mitochondrial function and cell survival. Since mitochondria play a key role in tumor cell proliferation, they represent a promising therapeutic target for cancer treatment. In this study, we characterized the impact of different IR sources on mitochondrial function in radioresistant cancer cells. Our findings revealed several adaptive responses that may contribute to radioresistance, including increased mtDNA content, mitochondrial mass, enhanced activity, and hyperfusion of the mitochondrial network. Notably, the use of mitochondrial-targeted G-quadruplex (G4) ligands, which block mtDNA replication and transcription, disrupted these responses, reducing cancer cell survival in an mtDNA-dependent manner. These results demonstrate that mitochondrial adaptations contribute to radioresistance and highlight mitochondria as a novel target for the radiosensitizing effects of G4-ligands, extending their potential beyond telomere destabilization.

cell biology↗

bioRxiv2022

Identification of key residues of the DNA glycosylase OGG1 controlling efficient DNA scanning and recruitment to oxidized bases in living cells

The DNA-glycosylase OGG1 oversees the detection and clearance of the 7,8-dihydro-8-oxoguanine (8-oxoG), which is the most frequent form of oxidized base in the genome. This lesion is deeply buried within the double-helix and its detection requires careful inspection of the bases by OGG1 via a mechanism that remains only partially understood. By analyzing OGG1 dynamics in the nucleus of living human cells, we demonstrate that the glycosylase constantly scans the DNA by rapidly alternating between diffusion within the nucleoplasm and short transits on the DNA. This scanning process, that we find to be tightly regulated by the conserved residue G245, is crucial for the rapid recruitment of OGG1 at oxidative lesions induced by laser micro-irradiation. Furthermore, we show that residues Y203, N149 and N150, while being all involved in early stages of 8-oxoG probing by OGG1 based on previous structural data, differentially regulate the scanning of the DNA and recruitment to oxidative lesions.

cell biology↗

bioRxiv2022

Loss of CD24 promotes radiation- and chemo-resistance by inducing stemness properties associated with a hybrid E/M state in breast cancer cells

There is compelling evidence that cancer stem cells (CSCs) play an essential role in failure of conventional antitumor therapy. In breast cancer, CD24-/low/CD44+ phenotype as well as a high aldehyde dehydrogenase activity (ALDH+) are widely associated with CSC subtypes. Furthermore, CD24-/low/CD44+ pattern is also characteristic of the mesenchymal cells generated by an epithelial-mesenchymal transition (EMT). CD24 is a surface marker expressed in many tumor types, however, its biological functions and role in cancer progression and treatment resistance remain poorly documented. We have previously shown that loss of CD24 expression in breast cancer cells is associated with radiation resistance, in relationship with the control of oxidative stress. Because ROS are known to mediate the effects of anticancer drugs as well as ionizing radiation, we investigated if CD24 could be defined as an actor of both radiation- and chemo-resistance of breast cancer cells. Using the HMLE breast cancer cell model, we observed that loss of CD24 expression induces stemness properties associated with the acquisition of a hybrid E/M phenotype. The CD24-/low cells were intrinsically more resistant than CD24+ cells. The resistance was linked to a lower level of ROS, and CD24 controlled ROS levels through the regulation of mitochondrial functions independently of antioxidant activity. Together, these results suggest a key role of CD24 in de-differentiation process of breast cancer cells, promoting acquisition of therapeutic resistance properties.

cancer biology↗

bioRxiv2020

DNA oxidation induced by fetal exposure to BPA agonists impairs female meiosis

Many endocrine disruptors have been proven to impair the meiotic process that is mandatory to produce healthy gametes. Bisphenol A is emblematic as it impairs meiotic prophase I and causes oocyte aneuploidy following in utero exposure. However, the mechanisms underlying these deleterious effects remain poorly understood. Furthermore, the increasing uses of BPA analogs raise concerns for public health. Here, we investigated the effect on oogenesis in mouse of fetal exposure to two BPA analogs, Bisphenol A Diglycidyl Ether (BADGE) or Bisphenol AF (BPAF). These analogs delay meiosis initiation, increase MLH1 foci per cell and induce oocyte aneuploidy. We further demonstrate that these defects are accompanied by a deregulation of gene expression and aberrant mRNA splicing in fetal premeiotic germ cells. Interestingly, we observed an increase in DNA oxidation after exposure to BPA analogs. Specific induction of oxidative DNA damages during fetal germ cell differentiation causes similar defects during oogenesis, as observed in 8-Oxoguanine DNA Glycosylase (OGG1) deficient mice or after in utero exposure to potassium bromate (KBrO3), an inducer of oxidative DNA damages. Moreover, the supplementation of N-acetylcysteine (NAC) with BPA analogs counteracts the bisphenol-induced meiotic effect. Together our results position oxidative stress as a central event that negatively impacts the female meiosis with major consequences on oocyte quality. This could be a common mechanism of action for so called endocrine disruptors pollutants and it could lead to novel strategies for reprotoxic compounds.

molecular biology↗

bioRxiv2018

MasterPATH: network analysis of functional genomics screening data

Functional genomics employs several experimental techniques to investigate gene functions. These techniques such as loss-of-function screening and transcriptome profiling performed in a high-throughput manner give as result a list of genes involved in the biological process of interest. There exist several computational methods for analysis and interpretation of the list. The most widespread methods aim at investigation of biological processes significantly represented in the list or at extracting significantly represented subnetworks. Here we present a new exploratory network analysis method that employs the shortest path approach and centrality measure to uncover members of active molecular pathways leading to the studied phenotype based on the results of functional genomics screening data. We present the method and we demonstrate what data can be retrieved by its application to the terminal muscle differentiation miRNA loss-of-function screening and transcriptomic profiling data and to the druggable loss-of-function RNAi screening data of the DNA repair process.

systems biology↗