Every day, many different types of DNA damage threaten the integrity of our genomes. Failure to properly repair DNA damage can result in chromosomal rearrangements and mutations that cause cancer or lead to cell death. In healthy cells, genome stability is safeguarded by multiple sophisticated responses that specifically detect, signal, and repair the damage.
The central goal of our research is to understand how responses to DNA damage are regulated and how their dysregulation by viruses promotes carcinogenesis in infected cells. Our findings generate important information and new areas of investigation in virology, as well as fundamental understanding of the pathways that safeguard genome stability in our cells. Ultimately, our work is important to understand how healthy cells and virally induced cancer cells respond to DNA-damaging agents used in cancer clinics.
Research in the laboratory focuses on three main areas:
1- Deciphering how viruses manipulate the DNA damage response
Viruses target the DNA repair machinery of host cells to either inhibit the innate immune response or to promote viral replication (Fradet-Turcotte and Weitzman, Annual Review Virology, 2018). We are interested in understanding how viral proteins hijack or impede DNA damage signaling and repair in cells. The E3 ubiquitin ligase RNF168 plays a key role in the DNA damage response. Studies from our laboratory revealed RNF168 as a common target of oncogenic viruses (e.g., human papillomavirus (HPV) and Epstein-Barr virus (EBV)). We have uncovered a new mechanism by which the HPV E7 oncoprotein hijacks the function of RNF168 and promotes oncogenesis (Sitz et al., PNAS, 2019). This study revealed that E7 compromises DNA repair pathway choice by directly interacting with RNF168. This finding is in line with the mutational signature observed in HPV-positive tumours by Dr. Higginson at Memorial Sloan Kettering Cancer Center (co-published with our study in PNAS; Leeman et al., PNAS, 2019).
In collaboration with Dr. Louis Flamand, we also defined the mechanisms by which human herpesvirus 6 (HHV-6) immediate-early 1 (IE1) protein inhibits DNA damage signaling (Collins, Biquand and Tremblay, EMBO Reports, 2024). Specifically, our concerted efforts revealed how two uncharacterized domains of HHV-6B IE1 simultaneously interact with NBS1 and inhibit ATM activation at double-strand breaks, leading to genome instability. These findings identified a new mode by which viruses manipulate DNA repair signaling upon infection.
2- Identifying the vulnerabilities of viral-induced cancers
We use CRISPR-based techniques to identify genes contributing to cell survival upon treatment with DNA interstrand crosslink (ICL) inducing agents. Recently, we discovered the protein FIRRM as a novel regulator of the ICL repair pathway. Further characterization of FIRRM and its interactor the AAA+ ATPase FIGNL1 revealed that it promotes the disassembly of RAD51 filaments at sites of DNA damage (Pinedo-Carpio, Dessapt et al., Science Advances, 2023; Stok et al., Cell Report 2023; Kuthethur et al., BioRxiv 2025). Our lab is currently characterizing how the formation of a complex between FIRRM and FIGNL1 contributes to DNA repair in different genetic backgrounds. A similar approach revealed that HPV-positive cancer cells do not rely on the canonical DNA repair pathways to resolve ICLs. Interestingly, characterization of these cells identified FIRRM as an essential component of cell survival in response to ICL-inducing agents, suggesting that HPV-positive cancer cells resist ICLs through an alternative mechanism. Current investigations in the laboratory aim to understand how HPV makes cancer cells deal with ICL-induced DNA replication stress.
3- Understanding how chromatin composition affects DNA damage signaling and repair
DNA damage signaling and repair are processes that occur on chromatin. DNA double-strand break (DSB) signaling and the response to replication stress rely on RNF168, which promotes the recruitment of DNA repair factors at DNA breaks by ubiquitylating histone H2A, a key component of chromatin. The specific recruitment of these DNA repair factors is essential in deciding which DNA repair pathway is used. Investigating how chromatin composition at the break impacts the interaction and recruitment of the repair factors to ubiquitylated H2A allows us to determine its contribution to DNA repair. To facilitate this, we have developed unique expertise in the use of reconstituted nucleosomes, which has allowed us to address key long-standing questions related to chromatin dynamics and DSB signaling. For example, our work has defined how the histone variant macroH2A1.2 regulates the specific recruitment of ubiquitylated chromatin readers at collapsed replication forks, and demonstrated that improper DNA repair pathway choice can be toxic at specific loci (Galloy et al., Front Cell Dev. Biol., 2021; Clerf et al., Front. Epigenet. Epigenom., 2024; Galloy et al. Mol. Cell, Revision requested). Our expertise with recombinant nucleosomes has also been instrumental in characterizing the specificity of chromatin-modifying enzymes and chromatin readers (Nat. Commun., 2022; Devoucoux et al., Cell Rep., 2022, Binda et al., Life Science Alliance, 2023; Yang et al., Science, 2024).
