Previous webinars > 6th webinar 12/13/2022

6th EDRA Webinar

December 13, 2022, from 3.30 to 5 pm CET

 

Dr. Philippe Pasero - The Institute of Human Genetics (Institut de Génétique Humaine, IGH) , a joint research unit CNRS - Université de Montpellier (UMR 9002)

 Philippe Pasero

Cellular responses to replication stress: from R-loops to inflammation and beyond

Replication stress (RS) commonly refers to alterations of fork progression caused by various events of endogenous or exogenous origin. Oncogenes such as RASV12 induce RS by increasing transcription-replication conflicts (TRCs), but the mechanisms involved remain poorly understood. TRCs could result from the presence of structures called R-loops that form during transcription and may act as roadblocks to replication. Alternatively, toxic R-loops could form as a consequence of fork arrest and interfere with replication restart. To discriminate between these two possibilities, we have analyzed fork arrest and restart in the absence of RNase H activity. These analyses showed that yeast and human cells fail to process and to restart arrested forks in the presence of persistent RNA:DNA hybrids. We propose that cotranscriptional R-loops are converted into toxic RNA:DNA hybrids upon fork passage, which interfere with fork restart. 

The expression of RASV12 in immortalized BJ fibroblasts promotes oncogene-induced senescence (OIS) by increasing RS and triggering inflammation. Interestingly, BJ cells adapt to RASV12-induced RS by overexpressing fork-associated components of the ATR-CHK1 pathway, such as Claspin and Timeless. Interestingly, these cells show a reduction in both RS and inflammation, suggesting that these processes are linked. To address this possibility, we have inhibited MRE11 in BJ-RASV12 cells and found that it completely suppressed OIS. Since MRE11 releases DNA fragments from stressed forks, these data suggest that MRE11 connects RS, inflammation and senescence by promoting the accumulation of immunogenic DNA fragments. This view is supported by the fact that inhibition of TREX1, the main exonuclease involved in the degradation of cytosolic DNA, is sufficient to induce replication stress and senescence, even in the absence of oncogenic stress. Altogether, these data indicate that MRE11 plays a central role in OIS by linking the replication stress response to inflammation.  

 

Short talk:

Umit Aliyaskarova - DNA Repair" group, CNRS UMR9019 Gustave Roussy, Université Paris-Saclay
 
Role of NEIL3 DNA glycosylase in the repair of cisplatin-induced DNA adducts 
Anti-neoplastic effect of DNA cross-linking agents such as cisplatin, mitomycin C, and psoralen is attributed to their ability to induce DNA interstrand crosslinks (ICLs), which block replication, transcription, and linear repair pathways by preventing DNA strand separation and trigger apoptosis. It is generally agreed that the Fanconi anemia (FA) pathway orchestrates the removal of ICLs by the combined actions of various DNA repair pathways. Recently, attention has been focused on the ability of the NEIL3-initiated base excision repair pathway to resolve psoralen- and abasic site-indced ICLs in an FA-independent manner. Intriguingly, overexpression of NEIL3 is associated with chemo-resistance and poor prognosis in many solid tumors. Here, using loss- and gain-of-function approaches we demonstrate that NEIL3 confers resistance to cisplatin and participates in the removal of cisplatin-DNA adducts. Proteomic studies reveal that the NEIL3 protein interacts with the 26S proteasome in a cisplatin-dependent manner. NEIL3 mediates proteasomal degradation of WRNIP1, a protein involved in the early step of ICL repair. We propose that NEIL3 participates in the repair of ICL-stalled replication fork by recruitment of the proteasome to ensure a timely transition from lesion recognition to repair via degradation of early-step proteins.
 
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