Función de PARP-1 en rutas de inestabilidad genómica e hipoxiaImplicaciones en el control tumoral

Resumen

Poly (ADP-ribose) polymerases (PARPs) constitute a family of enzymes involved in the regulation of many cellular processes such as DNA repair, gene transcription, cell cycle progression, cell death, chromatin functions and genomic stability. Among the 17 members identified so far, PARP-1 and PARP-2 are the only proteins stimulated by DNA strand breaks and implicated in the repair of DNA injury. Therefore, these molecules have been exploited as potential targets for the development of pharmacological strategies to increase the antitumor efficacy of chemotherapeutic agents, which induce DNA damage. The general aim of this research has been to place PARP-1 in the context of the tumor micro-environment studying both the response to ionising radiation, through its interaction with ATM, and its role in hypoxia. The presence of damaged DNA in the cell activates repair mechanisms as well as signal transduction pathways leading to cell cycle arrest and programmed cell death. The protein kinase ATM is centrally involved in the cellular response to ¿-irradiation (IR) and other DNA double strand breaks (DSBs)-inducing insults, whereas that poly(ADP-ribose)polymerase-1 (PARP-1) is involved mainly in base excision repair, a key pathway in the repair of DNA single strand breaks (SSBs). Here we report that ATM and PARP-1 form a molecular complex in vivo and that ATM is modified by PARP-1 during DNA damage by ¿-irradiation. We have also found that PARP-1 deficient cells or cells treated with PARP inhibitors display a defective ATM-kinase activity in response to IR. On the other hand, in the absence of PARP-1 activity, spontaneous non repaired single strand breaks collapse replication forks and trigger ATM for repair of DNA double strand breaks originated. So, PARP inhibitors induce ATM activation through DSBs formation to activate repair mechanisms. In ATM-deficient cells, double strand breaks originated can not be repaired via ATM, and as consequence there is an increased sensitivity and death cell provoked by PARP inhibitors. By other side, transcriptional responses to hypoxia are primarily mediated by the hypoxia-inducible factor (HIF), a heterodimer of HIF-¿ and HIF-ß subunits. In this study, we present evidence for a role of PARP-1 in the regulation of the hypoxic pathway. Furthermore, we show an impact of PARP-1 on the hypoxic activation of HIF. Therefore, we have studied two aspects of PARP-1 biology to contribute to our current knowledge of the role of PARP-1 in tumor development through genomic instability and hypoxia related-environment.