title: FANCD2-controlled chromatin access of the Fanconi-associated nuclease FAN1 is crucial for the recovery of stalled replication forks.
abstract: Fanconi anemia (FA) is a cancer predisposition syndrome characterized by cellular hypersensitivity to DNA interstrand cross-links (ICLs). Within the FA pathway, an upstream core complex monoubiquitinates and recruits the FANCD2 protein to ICLs on chromatin. Ensuing DNA repair involves the Fanconi-associated nuclease 1 (FAN1), which interacts selectively with monoubiquitinated FANCD2 (FANCD2(Ub)) at ICLs. Importantly, FANCD2 has additional independent functions: it binds chromatin and coordinates the restart of aphidicolin (APH)-stalled replication forks in concert with the BLM helicase, while protecting forks from nucleolytic degradation by MRE11. We identified FAN1 as a new crucial replication fork recovery factor. FAN1 joins the BLM-FANCD2 complex following APH-mediated fork stalling in a manner dependent on MRE11 and FANCD2, followed by FAN1 nuclease-mediated fork restart. Surprisingly, APH-induced activation and chromatin recruitment of FAN1 occur independently of the FA core complex or the FAN1 UBZ domain, indicating that the FANCD2(Ub) isoform is dispensable for functional FANCD2-FAN1 cross talk during stalled fork recovery. In the absence of FANCD2, MRE11 exonuclease-promoted access of FAN1 to stalled forks results in severe FAN1-mediated nucleolytic degradation of nascent DNA strands. Thus, FAN1 nuclease activity at stalled replication forks requires tight regulation: too little inhibits fork restart, whereas too much causes fork degradation.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Indrajit
authors.initials: I
authors.lastname: Chaudhury
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Stroik
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA asobeck@umn.edu.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Sobeck
mesh_terms: D016590:Aphidicolin / Q000494:pharmacology; D020134:Catalytic Domain; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D052236:Fanconi Anemia Complementation Group D2 Protein / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D000076228:MRE11 Homologue Protein; D064251:Multifunctional Enzymes; D053484:RecQ Helicases / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; C499905:FANCD2 protein, human; D052236:Fanconi Anemia Complementation Group D2 Protein; C121766:MRE11 protein, human; D064251:Multifunctional Enzymes; D016590:Aphidicolin; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C551063:FAN1 protein, human; D000076228:MRE11 Homologue Protein; C097151:Bloom syndrome protein; D053484:RecQ Helicases