The human AP-endonuclease 1 (APE1) is a DNA G-quadruplex structure binding protein and regulatesKRASexpression in pancreatic ductal adenocarcinoma cells

Abstract

Pancreatic ductal adenocarcinoma (PDAC), one of the most aggressive types of cancer, is characterized by aberrant activity of oncogenic KRAS. A nuclease-hypersensitive GC-rich region in KRAS promoter can fold into a four-stranded DNA secondary structure called G-quadruplex (G4), known to regulate KRAS expression. However, the factors that regulate stable G4 formation in the genome and KRAS expression in PDAC are largely unknown. Here, we show that APE1 (apurinic/apyrimidinic endonuclease 1), a multifunctional DNA repair enzyme, is a G4-binding protein, and loss of APE1 abrogates the formation of stable G4 structures in cells. Recombinant APE1 binds to KRAS promoter G4 structure with high affinity and promotes G4 folding in vitro. Knockdown of APE1 reduces MAZ transcription factor loading onto the KRAS promoter, thus reducing KRAS expression in PDAC cells. Moreover, downregulation of APE1 sensitizes PDAC cells to chemotherapeutic drugs in vitro and in vivo. We also demonstrate that PDAC patients’ tissue samples have elevated levels of both APE1 and G4 DNA. Our findings unravel a critical role of APE1 in regulating stable G4 formation and KRAS expression in PDAC and highlight G4 structures as genomic features with potential application as a novel prognostic marker and therapeutic target in PDAC.

STAT3 Inhibition Attenuates MYC Expression by Modulating Co-Activator Recruitment and Suppresses Medulloblastoma Tumor Growth by Augmenting Cisplatin Efficacy In Vivo

“…For IF, cells grown on coverslips were fixed with 4% formaldehyde (Sigma Aldrich, St. Louis, MO, USA) and stained as described previously [ 34 , 35 ]. The primary antibody used for IF was anti-H3K27Ac (1:50; CST #4353S).…”

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Sperm telomeres, oxidative stress, and infertility

“…The GQ cannot be reformed until the apurinic site has been fully repaired by AP endonuclease 1 (APEX1)(Wilson & Bohr 2007, Li & Wilson 2014 as depicted in Fig.2(adapted from DeRosa et al 2021). Recent studies confirm that loss of APE1 activity and/or APE1-AP site coordination abrogates GQ formation(Madlener et al 2013, Roychoudhury et al 2020, Pramanik et al 2022).…”

Protein-Scaffolded DNA Nanostructures for Imaging of Apurinic/Apyrimidinic Endonuclease 1 Activity in Live Cells

“…Human apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional enzyme that plays crucial roles in base excision repair and gene regulation. , As a base repair enzyme, APE1 recognizes and exerts an incision adjacent to 5′ of an abasic site, generating a nick in the phosphodiester backbone to initiate base repairing . APE1 is overexpressed in various cancer cells and has been identified as a diagnostic biomarker and therapeutic target. − Intracellular imaging of APE1 would provide useful information for cancer diagnosis, prognosis, and treatment evaluation.…”