Biology subjects

Dardillac, E.

Publications and source records attributed to Dardillac, E..

3 recordsLinked to original sources

bioRxiv2025

Dysregulation of replication stress-induced ROS in transformed cell lines: a vicious circle at cancer initiation

The canonical DNA damage response (DDR) maintains genome stability, involving DNA synthesis/cell cycle arrest. However, unchallenged cells proliferate when they are continually exposed to low-level/endogenous replication stress. We previously discovered and characterized a noncanonical cellular response that is specific to nonblocking replication stress, i.e., low-level stress (LoL-DDR), in primary cells. Although this response generates replication stress-induced reactive oxygen species (RIR), it triggers a program that prevents the accumulation of premutagenic 8-oxo-guanine (8-oxoG). Primary cells control RIR production via NADPH oxidases. Increasing the severity of replication stress above a precise threshold triggers the canonical DDR, leading to cell cycle arrest and RIR suppression, resulting in a peak-shaped dose response for RIR production. Here, we show that the LoL-DDR is dysregulated in cancer cell lines, which exhibit the following differences compared with primary cells: 1-RIR are not detoxified under high-level stress conditions, resulting in a continuous increase in the dose-response curve of RIR production; 2-RIR are not produced by NADPH oxidases; and 3-replication stress favors the accumulation of the premutagenic 8-oxoG. Moreover, using an in vitro breast cancer progression model, we show that LoL-DDR dysregulation occurs at an early stage of cancer progression. Since, conversely, ROS trigger replication stress this establishes a "vicious circle" involving replication-stress and ROS that continuously jeopardizes genome integrity that should fuel and amplify tumorigenesis.

cell biology↗

bioRxiv2020

An adaptive pre-DNA-damage-response protects genome integrity

The DNA damage response (DDR) interrupts cell cycle progression to restore genome integrity. However, unchallenged proliferating cells are continually exposed to endogenous stress, raising the question of a stress-threshold for DDR activation. Here, we identified a stress threshold below which primary human fibroblasts, activate a cell-autonomous response that not activates full DDR and not arrests cell cycle progression. We characterized this "pre-DDR" response showing that it triggers the production of reactive oxygen species (ROS) by the NADPH oxidases DUOX1 and DUOX2, under the control of NF-{kappa}B and PARP1. Then, replication stress-induced ROS (RIR) activates the FOXO1 detoxifying pathway, preventing the nuclear accumulation of the pre-mutagenic 8-oxoGuanine lesion, upon endogenous as well as exogenous pro-oxidant stress. Increasing the replication stress severity above the threshold triggers the canonical DDR, leading to cell cycle progression arrest, but also to RIR suppression. These data reveal that cells adapt their response to stress severity, unveiling a tightly regulated "pre-DDR" adaptive response that protects genome integrity without arresting cell cycle progression.

cell biology↗

bioRxiv2019

A homozygous hypomorphic BRCA2 variant causes primary ovarian insufficiency without cancer or Fanconi anemia traits.

Primary Ovarian insufficiency (POI) affects 1% of women under forty. We studied a patient with a non-syndromic POI, from a consanguineous Turkish family. Exome sequencing identified a homozygous missense variant c.8524C>T/p.R2842C in BRCA2. BRCA2 is a major player in homologous recombination (HR). BRCA2 deficiency induces cancer predisposition and Fanconi Anemia (FA). Remarkably, neither the patient nor her family exhibit somatic pathologies. The patients somatic cells presented intermediate levels of chromosomal breaks, cell proliferation and radiation-induced RAD51 foci formation when compared to controls, the heterozygous mothers and FA cells. R2842C-BRCA2 partially complemented BRCA2 depletion for double-strand break-induced HR. The residual HR function in patients cells could explain the absence of somatic pathology. BRCA2 is expressed in human fetal ovaries in pachytene stage oocytes, when meiotic HR occurs. This study has a major impact on the understanding of genome maintenance in somatic and meiotic cells and on the management of POI patients.

genetics↗