CIN-Independent cell death in S phase induced by Pol Eta depletion. Reunión conjunta 2020 SAIB-SAMIGE

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

Modalidad on-line

Congreso; Reunión Conjunta 2020 SAIB-SAMIGE; 2020

Sociedad Argentina de Investigación Bioquímica y Biología Molecular en conjunto con Asociación civil de microbiología general

In healthy cells, genomic stability is conserved by the coordinated activity of multiple genome maintenance pathways that ensure faithful DNA replication and equal distribution of the duplicated DNA among daughter cells. These pathways include DNA damage response (DDR) mechanisms, such as cell cycle checkpoints, DNA repair, and DNA damage tolerance, to name a few. Defects in DDR lead to genomic instability, a state with an increased tendency to acquire genetic alterations that may trigger tumorigenesis. Genomic instability can manifest as a higher rate of acquisition of gross numerical or structural changes in the chromosomes, known as chromosomal instability (CIN). CIN is triggered both by chromosome segregation errors during mitosis and replication stress during S and 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 to treatments, it is clear that it is recurrently elevated after DDR components´ inhibition. It has been proposed that the increase in CIN levels during cancer treatment should be pushed to the point that it is not anymore compatible with cell survival. An alternative, very challenging, and so-far under-explored strategy is to induce cell death without generating abrupt and acute changes in CIN levels.When evaluating the mechanisms of cell death after the elimination of a DNA polymerase (pol eta-h), a factor that is key to promote DNA replication across damaged DNA, we found that the depletion of pol eta exacerbates the cell death caused by DNA damaging agents without causing a concomitant increase in CIN. This particular response happens because, in the absence of Pol eta, cells cannot complete DNA replication and are more efficiently arrested in S phase. Soon after the DNA damaging challenge, cells depleted from pol eta display augmented double-strand breaks that persist over time. DSBs are followed by the accumulation of massive regions of ssDNA and pan-nuclear phosphorylation of histone H2AX, which has been shown to correlate with a commitment to cell death. We also found evidence of RPA exhaustion, a marker that characterizes cell death in S phase. Such results suggest that the modulation of specific DDR effectors could selectively promote cell death in S phase preventing CIN augmentation, a concept that may be relevant in clinical settings.