Zhou Xu (Institut de Biologie de Paris-Seine, CNRS), responsable de l'équipe "Télomère et Stabilité Génomique", invité par Human Rezaei

Functions of the Saccharomyces cerevisiae CST complex in double-strand break repair

Jeudi 6 juin 2024, à 11h

Summary

Following a double-strand break (DSB), resection is an important step that controls the repair pathway choice between homologous recombination and non-homologous end-joining (NHEJ). Telomeres are also subjected to resection, which is counteracted by the Ku and the Cdc13-Stn1-Ten1 (CST) complexes. Interestingly, the CST complex can localize at DSBs to promote de novo telomere formation. However, whether it contributes to DNA repair is not clear. Additionally, because of its essential function in telomere protection, the genetic approaches to study the question are limited.

Here, we circularized the single linear chromosome of an engineered yeast strain to generate a strain without telomeres and where the CST is no longer essential. We then used an inducible CRISPR/Cas9 system to create a single targeted DSB. We found that following DSB, survival is mostly NHEJ-dependent and significantly decreased without CST. Using resection assays, we found that CST limits the extent of single-stranded DNA by recruiting Pola-primase. Analysis of the break site after repair in surviving colonies revealed that the stn1∆ mutant showed a unique mutational signature with less deletions, in particular those involving microhomologies, than wild-type, suggesting a role both in NHEJ and microhomology-mediated repair.

By regulating single-stranded DNA, the CST complex might therefore regulate the choice between multiple DSB repair pathways.

Planning 2023/2024 des séminaires de la VIM