The structure-specific flap endonuclease 1 (FEN-1) is a multifunctional enzyme that participates in various activities such as DNA replication, DNA repair and apoptotic DNA fragmentation. Several mechanisms, including protein-protein interactions, sub-cellular compartmentalization and posttranslational modifications have been proposed to explain how FEN1 accomplishes these various activities. For example, the C-terminus of FEN1 has been shown to be acetylated by the histone acetyl transferase protein (HAT) p300 which is known to result in a significant reduction in the DNA binding and nuclease activities of FEN1. We now demonstrate that the NAD-dependent class III histone deacetylase SIRT1 physically interacts with FEN1 and that the opposing deacetylation by SIRT1 subsequently restores the endonuclease activity of FEN1. Moreover, clonogenicity experiments suggest that genetic knockdown of FEN1 or SIRT1 in cancer cells sensitizes those cells to irradiation treatment. This is of significance as it has been observed that increased SIRT1 levels protect mice from irradiation-induced cancer. Furthermore, we have also identified two nuclear shuttling proteins, Karyopherin α2 and Karyopherin β1 as interacting partners of both SIRT1 and FEN1. Using mass spectrometry, immunoprecipitation combined with subsequent western-blot analysis and confocal microscopy we demonstrate that, under basal conditions, a significant amount of both SIRT1 and FEN1 is located in the cytoplasm of cells. However, after induction of DNA damage by the methylating agent MMS, Karyopherin α2 and Karyopherin β1 mediate the translocation of SIRT1 and FEN1 into the nucleus in a time dependent manner. In summary we describe a novel interaction between SIRT1 and FEN1, demonstrate that acetylation/deacetylation regulates FEN1 activity and that the Karyopherins α2 and β1 mediate the nuclear import of SIRT1 and FEN1 following DNA damage. Our results suggest that inhibiting the nuclear import or activation of FEN1 or SIRT1 could represent potential anticancer strategies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4193. doi:10.1158/1538-7445.AM2011-4193

©2011 American Association for Cancer Research
2011