Fonctions de protéines télomériques dans la réparation de l'ADN // Functions of telomeric proteins in DNA repair

Genome integrity is constantly challenged by DNA damage, among which double-strand breaks (DSBs) are considered the most toxic. Following a DSB, the DNA damage response (DDR) ensures that appropriate cell fate decisions are made. The response is initiated by the resection of the 5 extremities of the DSB, exposing single-strand DNA (ssDNA), which controls the repair pathway choice between homologous recombination and non-homologous end-joining.
Telomeres, the extremities of eukaryotic chromosomes, resemble one side of a DSB but are protected by proteins that inhibit the DDR. In budding yeast, they include Rap1 and its cofactors on the double-stranded part of telomeres, and the Cdc13-Stn1-Ten1 (CST) complex binding to the single-stranded 3 overhang (Wellinger and Zakian 2012). CST functions at telomeres by protecting the overhang, assisting replication, counteracting resection and recruiting telomerase. Intriguingly, CST can localize at DSBs where it promotes de novo telomere formation. Recently, the human CST has also been involved in DSB processing and repair pathway choice (Barazas et al. 2018; Mirman et al. 2018; Mirman et al. 2022).
The main objective of this project is to investigate the functions of the CST complex at DSBs, especially in repair, without confounding effects from telomeres, in the yeast Saccharomyces cerevisiae. We propose that the fine regulation of ssDNA by CST is crucial for protection, repair pathway choice and genome stability. Specifically, this proposal aims at establishing the contribution of CST to repair pathways, at understanding how CST is regulated, and at solving how CST regulates ssDNA at the molecular level. To do so, the project will deploy a set of complementary approaches to dissect CST's functions. They include a strain with a circularized genome, hence no telomeres, where a Cas9-inducible DSB has been introduced and high-throughput genomic methods to measure the extent of ssDNA and fill-in process at the nucleotide resolution. Some of the experimental setups are already established in the lab and preliminary results show that CST mutants display altered DSB repair efficiency, notably less non-homologous end-joining-mediated repair events.
The project aims at shedding light onto the molecular functions of CST at DSB and its role in repair pathway choice.
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Genome integrity is constantly challenged by DNA damage, among which double-strand breaks (DSBs) are considered the most toxic. Following a DSB, the DNA damage response (DDR) ensures that appropriate cell fate decisions are made. The response is initiated by the resection of the 5 extremities of the DSB, exposing single-strand DNA (ssDNA), which controls the repair pathway choice between homologous recombination and non-homologous end-joining.
Telomeres, the extremities of eukaryotic chromosomes, resemble one side of a DSB but are protected by proteins that inhibit the DDR. In budding yeast, they include Rap1 and its cofactors on the double-stranded part of telomeres, and the Cdc13-Stn1-Ten1 (CST) complex binding to the single-stranded 3 overhang (Wellinger and Zakian 2012). CST functions at telomeres by protecting the overhang, assisting replication, counteracting resection and recruiting telomerase. Intriguingly, CST can localize at DSBs where it promotes de novo telomere formation. Recently, the human CST has also been involved in DSB processing and repair pathway choice (Barazas et al. 2018; Mirman et al. 2018; Mirman et al. 2022).
The main objective of this project is to investigate the functions of the CST complex at DSBs, especially in repair, without confounding effects from telomeres, in the yeast Saccharomyces cerevisiae. We propose that the fine regulation of ssDNA by CST is crucial for protection, repair pathway choice and genome stability. Specifically, this proposal aims at establishing the contribution of CST to repair pathways, at understanding how CST is regulated, and at solving how CST regulates ssDNA at the molecular level. To do so, the project will deploy a set of complementary approaches to dissect CST's functions. They include a strain with a circularized genome, hence no telomeres, where a Cas9-inducible DSB has been introduced and high-throughput genomic methods to measure the extent of ssDNA and fill-in process at the nucleotide resolution. Some of the experimental setups are already established in the lab and preliminary results show that CST mutants display altered DSB repair efficiency, notably less non-homologous end-joining-mediated repair events.
The project aims at shedding light onto the molecular functions of CST at DSB and its role in repair pathway choice.
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Début de la thèse : 01/10/2025

Contrat doctoral

Concours pour un contrat doctoral

Sorbonne Université SIM (Sciences, Ingénierie, Médecine)

515 Complexité du vivant

The project would be ideal for a candidate with a background in biology, more specifically in molecular biology or genetics. Basic (or advanced) bioinformatics skills will be important as well.
The project would be ideal for a candidate with a background in biology, more specifically in molecular biology or genetics. Basic (or advanced) bioinformatics skills will be important as well.