title: Structural insights into 5' flap DNA unwinding and incision by the human FAN1 dimer.
abstract: Human FANCD2-associated nuclease 1 (FAN1) is a DNA structure-specific nuclease involved in the processing of DNA interstrand crosslinks (ICLs). FAN1 maintains genomic stability and prevents tissue decline in multiple organs, yet it confers ICL-induced anti-cancer drug resistance in several cancer subtypes. Here we report three crystal structures of human FAN1 in complex with a 5' flap DNA substrate, showing that two FAN1 molecules form a head-to-tail dimer to locate the lesion, orient the DNA and unwind a 5' flap for subsequent incision. Biochemical experiments further validate our model for FAN1 action, as structure-informed mutations that disrupt protein dimerization, substrate orientation or flap unwinding impair the structure-specific nuclease activity. Our work elucidates essential aspects of FAN1-DNA lesion recognition and a unique mechanism of incision. These structural insights shed light on the cellular mechanisms underlying organ degeneration protection and cancer drug resistance mediated by FAN1.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Xue
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Simonne
authors.initials: S
authors.lastname: Longerich
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Sung
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Xiong
mesh_terms: D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004706:Endodeoxyribonucleases; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D008958:Models, Molecular; D064251:Multifunctional Enzymes; D009154:Mutation; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D064251:Multifunctional Enzymes; D011994:Recombinant Proteins; D004247:DNA; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C551063:FAN1 protein, human