Elevated level of acetylation of APE1 in tumor cells modulates DNA damage repair

Abstract

Apurinic/apyrimidinic (AP) sites are frequently generated in the genome by spontaneous depurination/depyrimidination or after removal of oxidized/modified bases by DNA glycosylases during the base excision repair (BER) pathway. Unrepaired AP sites are mutagenic and block DNA replication and transcription. The primary enzyme to repair AP sites in mammalian cells is AP endonuclease (APE1), which plays a key role in this repair pathway. Although overexpression of APE1 in diverse cancer types and its association with chemotherapeutic resistance are well documented, alteration of posttranslational modification of APE1 and modulation of its functions during tumorigenesis are largely unknown. Here, we show that both classical histone deacetylase HDAC1 and NAD+-dependent deacetylase SIRT1 regulate acetylation level of APE1 and acetylation of APE1 enhances its AP-endonuclease activity both in vitro and in cells. Modulation of APE1 acetylation level in cells alters AP site repair capacity of the cell extracts in vitro. Primary tumor tissues of diverse cancer types have higher level of acetylated APE1 (AcAPE1) compared to adjacent non-tumor tissue and exhibit enhanced AP site repair capacity. Importantly, in the absence of APE1 acetylation, cells accumulate AP sites in the genome and show increased sensitivity to DNA damaging agents. Together, our study demonstrates that elevation of acetylation level of APE1 in tumor could be a novel mechanism by which cells handle the elevated levels of DNA damages in response to genotoxic stress and maintain sustained proliferation.

Resveratrol decreases the expression of genes involved in inflammation through transcriptional regulation

“…APE1/Ref-1 is acetylated by p300, which increases its interaction with HDAC1 and its binding capacity for gene promoters [69,70]. Sengupta et al (2016) demonstrated the HDAC1 ability to catalyze the deacetylation of acetylated APE1/Ref-1 in vitro. These authors generated AcAPE1 by incubation with purified recombinant wild type APE1/ Ref-1 with p300 HAT domain, and confirmed acetylation by WB analysis using AcAPE1 specific antibody.…”

“…These authors generated AcAPE1 by incubation with purified recombinant wild type APE1/ Ref-1 with p300 HAT domain, and confirmed acetylation by WB analysis using AcAPE1 specific antibody. In addition, the incubation of AcAPE1 with affinity-purified FLAG-HDACs was carried out, which showed the action of HDAC1 [71]. This deacetylase is also stimulated by RESV (reviewed in [20]).…”

Nanoparticle-mediated knockdown of DNA repair sensitizes cells to radiotherapy and extends survival in a genetic mouse model of glioblastoma

“…This would suggest that this smaller surviving cell population in these tumors relied on additional DNA repair pathways to promote survival and increased aggression, or that there were alterations to remaining Ape1 acetylation that promoted enhanced AP-endonuclease activity. 44 Future studies should identify multiple DNA repair pathways to inhibit simultaneously to increase initial cell kill and reduce the proportion of recurrent cell survival.…”

Regulation of Oxidized Base Repair in Human Chromatin by Posttranslational Modification

“…While acetylation of APE1 enhances its stability in chromatin and enzymatic activity [135,136], CDK5-mediated phosphorylation enhances its ubiquitination and degradation [137,138]. Thus, it is possible that phosphorylation and acetylation are mutually exclusive, acetylation stabilizing the protein, and phosphorylation guiding to its degradation.…”