Biology subjects

Chapuis, C.

Publications and source records attributed to Chapuis, C..

5 recordsLinked to original sources

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↗

bioRxiv2024

Single-nucleosome imaging reveals principles of transient multiscale chromatin unfolding triggered by histone ADP-ribosylation at DNA lesions

Timely access to DNA lesions is crucial for genome integrity. This process requires profound remodeling of densely packed chromatin to establish a repair-competent architecture. However, limited resolution has made it impossible to fully understand these remodeling events. Here, combining microirradiation with live-cell multiscale imaging, we report that DNA damage-induced changes in genome packing rely on the conformational behaviour of the chromatin fiber. Immediately after damage, a transient increase in nucleosome mobility switches chromatin from a densely-packed state to a looser conformation, making it accessible to repair. While histone poly-ADP-ribosylation is required to trigger this switch, mono-ADP-ribosylation is sufficient to maintain the open-chromatin state. The removal of these histone marks by the ARH3 hydrolase then leads to chromatin recondensation. Together, our multiscale study of chromatin dynamics establishes a global model: distinct waves of histone ADP-ribosylation control nucleosome mobility, triggering a transient breathing of chromatin, crucial for initiating the DNA damage response.

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↗

bioRxiv2021

HPF1-dependent histone ADP-ribosylation triggers chromatin relaxation to promote the recruitment of repair factors at sites of DNA damage

PARP1 activity is regulated by its cofactor HPF1. The binding of HPF1 on PARP1 controls the grafting of ADP-ribose moieties on serine residues of proteins nearby the DNA lesions, mainly PARP1 and histones. However, the impact of HPF1 on DNA repair regulated by PARP1 remains unclear. Here, we show that HPF1 controls both the number and the length of the ADP-ribose chains generated by PARP1 at DNA lesions. We demonstrate that HPF1-dependent histone ADP-ribosylation, rather than auto-modification of PARP1, triggers the rapid unfolding of the chromatin structure at the DNA damage sites and promotes the recruitment of the repair factors CHD4 and CHD7. Together with the observation that HPF1 contributes to efficient repair both by homologous recombination and non-homologous end joining, our findings highlight the key roles played by this PARP1 cofactor at early stages of the DNA damage response.

cell biology↗

bioRxiv2019

Optimised FRET pairs and quantification approaches to detect the activation of Aurora kinase A at mitosis

Genetically-encoded Forsters Resonance Energy Transfer (FRET) biosensors are indispensable tools to sense the spatiotemporal dynamics of signal transduction pathways. Investigating the crosstalk between different signalling pathways is becoming increasingly important to follow cell development and fate programs. To this end, FRET biosensors must be optimised to monitor multiple biochemical activities simultaneously and in single cells. In addition, their sensitivity must be increased to follow their activation even when the abundance of the biosensor is low. We describe here the development of a second generation of Aurora kinase A/AURKA biosensors. First, we adapt the original AURKA biosensor -GFP-AURKA-mCherry- to multiplex FRET by using dark acceptors as ShadowG or ShadowY. Then, we use the novel superYFP acceptor protein to measure FRET by 2-colour Fluorescence Cross-Correlation Spectroscopy, in cytosolic regions where the abundance of AURKA is extremely low and undetectable with the original AURKA biosensor. These results pave the way to the use of FRET biosensors to follow AURKA activation in conjunction with substrate-based activity biosensors. In addition, they open up the possibility of tracking the activation of small pools of AURKA and its interaction with novel substrates, which would otherwise remain undetectable with classical biochemical approaches.

cell biology↗