Biology subjects

Medina-Suarez, S.

Publications and source records attributed to Medina-Suarez, S..

3 recordsLinked to original sources

bioRxiv2024

Continuous nuclear envelope surveillance is required for DNA double-strand break repair.

Precise double-strand break (DSB) repair is paramount for genome stability. Homologous recombination (HR) is preferred to repair DSBs when a nearby sister chromatid ensures an error-free template. In Saccharomyces cerevisiae, this preference extends into anaphase and telophase (late mitosis; late-M), despite sister chromatids having been pulled apart. Previously, we identified the nuclear envelope (NE) protein Msc1 as important for late-M DSB repair. Here, we report that Msc1 faces the NE lumen, and its depletion leads to DSB-independent over-compartmentalization of the nucleus, which hampers approximation of sister loci after DSB. Depletion of Msc1 also leads to nuclear pore complex mislocation, a phenotype shared by the highly conserved NE healing complex ESCRT-III. Critically, we show that both Msc1 and ESCRT-III also ensure DSB repair in G2/M, and that there is synergism between Msc1 and the ESCRT-III subunit Snf7. These findings highlight the essential role of NE health in DSB repair.

cell biology↗

bioRxiv2023

Msc1 is a nuclear envelope protein that reinforces DNA repair in late mitosis.

Precise double-strand break (DSB) repair is paramount for genome stability. Homologous recombination (HR) repairs DSBs when cyclin-dependent kinase (CDK) activity is high, which correlates with the availability of the sister chromatid as a template. However, anaphase and telophase are paradoxical scenarios since high CDK favors HR despite sister chromatids being no longer aligned. To identify factors specifically involved in DSB repair in late mitosis, we have undertaken comparative proteomics in Saccharomyces cerevisiae and found that Msc1, a poorly characterized nuclear envelope protein, is significantly enriched upon both random and guided DSBs. We further show that {Delta}msc1 is more sensitive to DSBs in late mitosis, and has a delayed repair of DBSs, as indicated by increased Rad53 hyperphosphorylation, fewer Rad52 repair factories, and slower HR completion. We discuss how Msc1 may favor the formation of Rad52 factories and the timely completion of HR before cytokinesis.

molecular biology↗

bioRxiv2020

Topoisomerase II deficiency leads to a postreplicative structural shift in all Saccharomyces cerevisiae chromosomes.

The key role of Topoisomerase II (Top2) is the removal of topological intertwines between sister chromatids. In yeast, inactivation of Top2 brings about distinct cell cycle responses. In the case of the conditional top2-5 allele, interphase and mitosis progress on schedule but cells suffer from a segregation catastrophe. We here show that top2-5 chromosomes fail to enter a Pulsed-Field Gel Electrophoresis (PFGE) in the first cell cycle, a behavior traditionally linked to the presence of replication and recombination intermediates. We distinguished two classes of affected chromosomes: the rDNA-bearing chromosome XII, which fails to enter a PFGE at the beginning of S-phase, and all the other chromosomes, which fail at a postreplicative stage. In synchronously cycling cells, this late PFGE retention is observed in anaphase; however, we demonstrate that this behavior is independent of cytokinesis, stabilization of anaphase bridges, spindle pulling forces and even anaphase onset. Strikingly, once the PFGE retention has occurred it becomes refractory to Top2 re-activation. DNA combing, two-dimensional electrophoresis, genetic analyses and GFP-tagged DNA damage markers suggest that non-recombinational modifications of late replication intermediates may account for the shift in the PFGE behavior. The fact that this shift does not trigger G2/M checkpoints further supports this statement since checkpoints are active for other replicative stresses in the absence of Top2. We propose that the prolonged absence of Top2 activity leads to a general chromosome structural change. This change might interlock chromatids together with catenations and thus contribute to the formation of anaphase bridges in top2 mutants.

molecular biology↗