5fv7
Human Fen1 in complex with an N-hydroxyurea compound
Structural highlights
FunctionFEN1_HUMAN Structure-specific nuclease with 5'-flap endonuclease and 5'-3' exonuclease activities involved in DNA replication and repair. During DNA replication, cleaves the 5'-overhanging flap structure that is generated by displacement synthesis when DNA polymerase encounters the 5'-end of a downstream Okazaki fragment. It enters the flap from the 5'-end and then tracks to cleave the flap base, leaving a nick for ligation. Also involved in the long patch base excision repair (LP-BER) pathway, by cleaving within the apurinic/apyrimidinic (AP) site-terminated flap. Acts as a genome stabilization factor that prevents flaps from equilibrating into structurs that lead to duplications and deletions. Also possesses 5'-3' exonuclease activity on nicked or gapped double-stranded DNA, and exhibits RNase H activity. Also involved in replication and repair of rDNA and in repairing mitochondrial DNA.[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedThe structure-specific nuclease human flap endonuclease-1 (hFEN1) plays a key role in DNA replication and repair and may be of interest as an oncology target. We present the crystal structure of inhibitor-bound hFEN1, which shows a cyclic N-hydroxyurea bound in the active site coordinated to two magnesium ions. Three such compounds had similar IC50 values but differed subtly in mode of action. One had comparable affinity for protein and protein-substrate complex and prevented reaction by binding to active site catalytic metal ions, blocking the necessary unpairing of substrate DNA. Other compounds were more competitive with substrate. Cellular thermal shift data showed that both inhibitor types engaged with hFEN1 in cells, and activation of the DNA damage response was evident upon treatment with inhibitors. However, cellular EC50 values were significantly higher than in vitro inhibition constants, and the implications of this for exploitation of hFEN1 as a drug target are discussed. Cellularly active N-hydroxyurea FEN1 inhibitors block substrate entry to the active site.,Exell JC, Thompson MJ, Finger LD, Shaw SJ, Debreczeni J, Ward TA, McWhirter C, Sioberg CL, Molina DM, Abbott WM, Jones CD, Nissink JW, Durant ST, Grasby JA Nat Chem Biol. 2016 Aug 15. doi: 10.1038/nchembio.2148. PMID:27526030[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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