title: Amino acid Asp181 of 5'-flap endonuclease 1 is a useful target for chemotherapeutic development.
abstract: DNA alkylation-induced damage is one of the most efficacious anticancer therapeutic strategies. Enhanced DNA alkylation and weakened DNA repair capacity in cancer cells are responsible for the effectiveness of DNA-alkylating therapies. 5'-Flap endonuclease 1 (Fen1) is an important enzyme involved in base excision repair (BER), specifically in long-patch BER (LP-BER). Using the site-directed mutagenesis approach, we have identified an important role for amino acid Asp181 of Fen1 in its endonuclease activity. Asp181 is thought to be involved in Mg(2+) binding in the active site. Using structure-based molecular docking of Fen1 targeted to its metal binding pocket M2 (Mg(2+) site), we have identified a potent low-molecular weight inhibitor (LMI, NSC-281680) that efficiently blocks LP-BER. In this study, we have demonstrated that the interaction of this LMI with Fen1 blocked its endonuclease activity, thereby blocking LP-BER and enhancing the cytotoxic effect of DNA-alkylating agent Temozolomide (TMZ) in mismatch repair (MMR)-deficient and MMR-proficient colon cancer cells. The results further suggest that blockade of LP-BER by NSC-281680 may bypass other drug resistance mechanisms such as mismatch repair (MMR) defects. Therefore, our findings provide groundwork for the development of highly specific and safer structure-based small molecular inhibitors targeting the BER pathway, which can be used along with existing chemotherapeutic agents, like TMZ, as combination therapy for the treatment of colorectal cancer.
authors.affiliation: Department of Anatomy and Cell Biology and UF Shands Cancer Center, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: Harekrushna
authors.initials: H
authors.lastname: Panda
authors.forename: Aruna S
authors.initials: AS
authors.lastname: Jaiswal
authors.forename: Patrick E
authors.initials: PE
authors.lastname: Corsino
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Armas
authors.forename: Brian K
authors.initials: BK
authors.lastname: Law
authors.forename: Satya
authors.initials: S
authors.lastname: Narayan
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry* / Q000235:genetics; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000378:metabolism; D004260:DNA Repair; D004791:Enzyme Inhibitors / Q000494:pharmacology; D045585:Flap Endonucleases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008958:Models, Molecular; D013329:Structure-Activity Relationship
chemical_list: D004791:Enzyme Inhibitors; D001224:Aspartic Acid; D045585:Flap Endonucleases