title: APE1 polymorphic variants cause persistent genomic stress and affect cancer cell proliferation.
abstract: Apurinic/apyrimidinic endonuclease 1 (APE1) is the main mammalian AP-endonuclease responsible for the repair of endogenous DNA damage through the base excision repair (BER) pathway. Molecular epidemiological studies have identified several genetic variants associated with human diseases, but a well-defined functional connection between mutations in APE1 and disease development is lacking. In order to understand the biological consequences of APE1 genetic mutations, we examined the molecular and cellular consequences of the selective expression of four non-synonymous APE1 variants (L104R, R237C, D148E and D283G) in human cells. We found that D283G, L104R and R237C variants have reduced endonuclease activity and impaired ability to associate with XRCC1 and DNA polymerase β, which are enzymes acting downstream of APE1 in the BER pathway. Complementation experiments performed in cells, where endogenous APE1 had been silenced by shRNA, showed that the expression of these variants resulted in increased phosphorylation of histone H2Ax and augmented levels of poly(ADP-ribosyl)ated (PAR) proteins. Persistent activation of DNA damage response markers was accompanied by growth defects likely due to combined apoptotic and autophagic processes. These phenotypes were observed in the absence of exogenous stressors, suggesting that chronic replication stress elicited by the BER defect may lead to a chronic activation of the DNA damage response. Hence, our data reinforce the concept that non-synonymous APE1 variants present in the human population may act as cancer susceptibility alleles.
authors.affiliation: Laboratory of Molecular Biology and DNA Repair, Department of Medical and Biological Sciences, University of Udine, 33100 Udine, Italy.|Department of Clinical Molecular Biology, University of Oslo and Akershus University Hospital, 1474 Nordbyhagen, Norway.
authors.forename: Lisa
authors.initials: L
authors.lastname: Lirussi
authors.affiliation: Laboratory of Molecular Biology and DNA Repair, Department of Medical and Biological Sciences, University of Udine, 33100 Udine, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Antoniali
authors.affiliation: Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, 80147 Naples, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: D'Ambrosio
authors.affiliation: Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, 80147 Naples, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.affiliation: Department of Clinical Molecular Biology, University of Oslo and Akershus University Hospital, 1474 Nordbyhagen, Norway.
authors.forename: Hilde
authors.initials: H
authors.lastname: Nilsen
authors.affiliation: Laboratory of Molecular Biology and DNA Repair, Department of Medical and Biological Sciences, University of Udine, 33100 Udine, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Tell
mesh_terms: D049109:Cell Proliferation / Q000235:genetics; D004260:DNA Repair / Q000235:genetics*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005838:Genotype; D006367:HeLa Cells; D006801:Humans; D009369:Neoplasms / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide
chemical_list: C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase
keywords: APE1/Ref-1; genetic variants; genotoxic damage; replication stress