PROJECT SUPERVISOR

Marie-Noëlle Simon

TEAM LEADER

Stéphane Coulon

Project members :

Karel Naiman
Researcher

Yves Corda
Researcher

Dmitri Churikov
Engineer

Asako Isogawa
Engineer

Manon Pierre
Engineer

Léa Seban
Doctoral student

Telomeres are nucleo-protein structures that protect the ends of chromosomes from degradation, fusion and illegitimate recombination. They consist of repeated DNA sequences that form a particular chromatin structure through specific DNA-protein interactions. Telomeres are known to be natural regions of the genome that are difficult to replicate, also defined as fragile sites due to the numerous obstacles that prevent the progression of replication forks at terminal sequences. Replicative stress at this level is due to the pausing or blocking of replication forks. This is a potential source of telomere dysfunction, which can lead to genome instability, a characteristic of cancer cells.

Recent discoveries

In recent years, we have shown how components of the yeast shelterin complex (telomeric proteins) recruit accessory factors to promote efficient replication of terminal sequences (Matmati et al., 2018& 2020; Vaurs et al., 2022). Our laboratory has also spearheaded efforts to show how stalled replication forks and eroded telomeres are relocated to the nuclear pore (NPC) to promote either precise replication resumption (Aguilera et al., 2020), or alternative telomere elongation based on recombination in the absence of telomerase (Churikov et al., 2016; Charifi et al., 2021; Aguilera et al., 2022).

The laboratory has also pioneered the description of the role of RPA in telomere replication, maintenance and recombination in yeast models (Maestroni et al. 2020; Corda et al., 2021; Audry et al., 2015).

Replication barrier analysis

We are analyzing the dynamics of replication at these barriers and identifying the proteome of telomere-arrested forks under different genetic conditions.

TEAM LEADER

Stéphane Coulon

Project members :

Frédéric Jourquin
Engineer

Valeria Rubeo
Doctoral student

Asako Isogawa
Engineer

Telomere syndromes are rare monogenic diseases characterized by premature telomere shortening. These syndromes give rise to the bone marrow failure syndrome Dyskeratosis Congenita (DC), aplastic anemia and idiopathic pulmonary fibrosis (IPF), which can be caused by telomere shortening and a reduction in the replicative potential of stem cells. In around 40% of cases, these telomere-shortening diseases are not genetically characterized.

Establishing the causal link

To establish the causal link between mutations in RPA (and also other candidate genes), and telomere instability and disease, we are introducing patient mutations into human cell lines using CrisPr-Cas9 technology and studying their effect on telomere stability. Our aim is to demonstrate the causality of patient mutations on telomere dysfunction, genome instability and TBD.

PROJECT SUPERVISOR

Alexandre de Nonneville

Project members :

Dmitri Churikov
Engineer

Jérome Robin
Researcher

Coline Hamelin
Engineer

Osteosarcomas are highly aggressive bone tumours that mainly occur in children and adolescents. Genetically, they are characterized by complex structural and numerical aberrations. Osteosarcomas are known to exhibit a high frequency of ALT (Alternative Lengthening of Telomeres) activation.

Mechanism study

We are investigating the mechanisms of ALT osteosarcoma.

PROJECT SUPERVISOR

Valérie Garcia

Project members :

Christelle Cayrou
Researcher

Pierre Luciano
Researcher

DNA double-strand breaks (DSBs) are a major threat to genome stability, as they can lead to mutations, chromosomal rearrangements and cancers. Paradoxically, during meiosis, these potentially dangerous lesions are programmed to initiate homologous recombination (HR), a repair process essential for accurate chromosome segregation and genetic diversity.

Our previous work has made significant contributions in this area (Garcia et al, Nature 2011; Garcia et al, Nature 2015).

Recent discoveries

Meiotic CBDs are formed by Spo11 in certain areas of the genome called "hotspots", which coincide with gene promoters. We have demonstrated that double cuts can occur simultaneously within hotspots. These "double cuts" (DCs) create "gaps" in the DNA, repaired by RH. Although our work was carried out on the yeast model S. cerevisiae, our research has shown that DCs are detected in mice and could represent a general feature of meiotic recombination.

➜ "Concerted cutting by Spo11 illuminates meiotic DNA break mechanics".. Johnson D, Crawford M, Cooper T, Claeys Bouuaert C, Keeney S, Llorente B, Garcia V*, Neale MJ*. Nature, 2021 *co-corresponding

➜ "Tel1 is recruited at chromosomal loop/axis contact sites to regulate meiotic DNA double-strand breaks interference.". Dorme M, Aithal R, Cayrou C, Luciano P, Vernerey J, Borde V, Llorente B *, Garcia V *. *co-corresponding - under revisions

Research in progress

In humans, mutations in the ATM gene are the cause ofataxia telangiectasia (AT), a genetic disease characterized by a predisposition to cancer and infertility (among other phenotypes). Mutations affecting the kinase domain are particularly harmful in AT patients and mouse models. However, the reason for the more severe effect of ATM "kinase dead" mutations remains unknown.

Our unpublished work demonstrates that inactivation of Tel1/ATM kinase activity, rather than total loss of the Tel1 protein, causes severe deregulation of meiotic CBD formation in S. cerevisiae. We have identified Tel1 interactors involved in this process and are currently investigating the underlying mechanisms.