CIN-independent cell death in S phase induced by pol eta depletion

SEBASTIÁN OMAR SIRI; FEDERICO, MARÍA BELÉN; CALZETTA, NICOLÁS LUIS; MARTINO, JULIETA; MARIA BELEN DE LA VEGA; VANESA GOTTIFREDI

Virtual (Pandemia)

Congreso; congreso conjunto SAIB-SAMIGE; 2020

SAIB-SAMIGE

COMUNICACIÓN ORALInhealthy cells, genomic stability is conserved by the coordinated activity ofmultiple genome maintenance pathways that ensure faithful DNA replication andequal distribution of the duplicated DNA among daughter cells. These pathwaysinclude DNA damage response (DDR) mechanisms, such as cell cycle checkpoints,DNA repair, and DNA damage tolerance, to name a few. Defects in DDR lead togenomic instability, a state with an increased tendency to acquire geneticalterations that may trigger tumorigenesis. Genomic instability can manifest asa higher rate of acquisition of gross numerical or structural changes in thechromosomes, known as chromosomal instability (CIN). CIN is triggered both bychromosome segregation errors during mitosis and replication stress during Sand M phase and is very frequent after treatments that impair DDR pathways.While it is unclear if CIN is associated with the development of resistance totreatments, it is clear that it is recurrently elevated after DDR components´inhibition. It has been proposed that the increase in CIN levels during cancertreatment should be pushed to the point that it is not anymore compatible withcell survival. An alternative, very challenging, and so-far under-exploredstrategy is to induce cell death without generating abrupt and acute changes inCIN levels. When evaluating the mechanisms of cell death after the eliminationof a DNA polymerase (pol eta-h),a factor that is key to promote DNA replication across damaged DNA, we foundthat the depletion of pol eta exacerbates the cell death caused by DNA damagingagents without causing a concomitant increase in CIN. This particular responsehappens because, in the absence of Pol eta, cells cannot complete DNAreplication and are more efficiently arrested in S phase. Soon after the DNAdamaging challenge, cells depleted from pol eta display augmented double-strandbreaks that persist over time. DSBs are followed by the accumulation of massiveregions of ssDNA and pan-nuclear phosphorylation of histone H2AX, which hasbeen shown to correlate with a commitment to cell death. We also found evidenceof RPA exhaustion, a marker that characterizes cell death in S phase. Suchresults suggest that the modulation of specific DDR effectors could selectivelypromote cell death in S phase, preventing CIN augmentation, a concept that maybe relevant in clinical settings