Independent Molecular Pathways Control Cell Survival and Genomic Stability after Ultraviolet Irradiation.

FEDERICO MB, PAVIOLO NS, CAMPODÓNICO P, CAMPANA, MC, VALLERGA MB, GOTTIFREDI V

Conferencia; 46th Annual Meeting of the Brazilian Society of Biochemistry and Molecular Biology; 2017

Independent Molecular Pathways Control Cell Survival and Genomic Stability after Ultraviolet IrradiationFederico, M.B.1, Paviolo, N.1, Campodónico, P.1, Campana, M.C.1, Vallerga,M.B.1, Gottifredi, V.1.The DNA Damage Response (DDR) is a network of pathways activated by the accumulation of DNA lesion. Our current understanding of DDR indicates thatsuch pathways work as progressive lines of defense, with some pathways beingactivated after a previous one. For example, Translesion DNA synthesis (TLS) bypol, a DNA polymerase which utilizes UV-damaged DNA as replicationtemplates, is considered to be an early line of defense after Ultraviolet radiation (UV). A failure to achieve TLS may trigger the accumulation of replication-associated double strand breaks (DSBs). Such derived-DNA lesion should be resolved by a second line of defense, Homologous recombination (HR) which can be stimulated by the Fanconi Anemia protein, FANCD2 and its cofactors. To test the progressive defense model for DDR activation, we disrupted the function of poleta and FANCD2 in different UV-irradiated cellular models. We observed that the DDR network does not activate pathways with sequential temporality. A defect in poleta activation causes the accumulation of replication stress markers such as pannuclear H2AX and 53BP1 and alters S phase progression while FANCD2 depletion does not affect such parameters. Furthermore, poleta exclusively control a cell death pathway associated with the exhaustion of a single stranded DNA binding protein; RPA. Conversely, FANCD2 is dispensable for cell death but prevents the accumulation of micronuclei and chromosomal aberrations in a manner that is independent from RPA and pol. Strikingly, the combined depletion of both proteins confirmed that each pathway contributes exclusively to either cell survival or to the genomic instability parameters evaluated in this study. Our findings demonstrate that distinct DDR pathways may independently control cell death and genomic instability, a property that should be exploited in the design of therapies.