title: CtIP mediates replication fork recovery in a FANCD2-regulated manner.
abstract: Fanconi anemia (FA) is a chromosome instability syndrome characterized by increased cancer predisposition. Within the FA pathway, an upstream FA core complex mediates monoubiquitination and recruitment of the central FANCD2 protein to sites of stalled replication forks. Once recruited, FANCD2 fulfills a dual role towards replication fork recovery: (i) it cooperates with BRCA2 and RAD51 to protect forks from nucleolytic degradation and (ii) it recruits the BLM helicase to promote replication fork restart while suppressing new origin firing. Intriguingly, FANCD2 and its interaction partners are also involved in homologous recombination (HR) repair of DNA double-strand breaks, hinting that FANCD2 utilizes HR proteins to mediate replication fork recovery. One such candidate is CtIP (CtBP-interacting protein), a key HR repair factor that functions in complex with BRCA1 and MRE11, but has not been investigated as putative player in the replication stress response. Here, we identify CtIP as a novel interaction partner of FANCD2. CtIP binds and stabilizes FANCD2 in a DNA damage- and FA core complex-independent manner, suggesting that FANCD2 monoubiquitination is dispensable for its interaction with CtIP. Following cellular treatment with a replication inhibitor, aphidicolin, FANCD2 recruits CtIP to transiently stalled, as well as collapsed, replication forks on chromatin. At stalled forks, CtIP cooperates with FANCD2 to promote fork restart and the suppression of new origin firing. Both functions are dependent on BRCA1 that controls the step-wise recruitment of MRE11, FANCD2 and finally CtIP to stalled replication forks, followed by their concerted actions to promote fork recovery.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Jung Eun
authors.initials: JE
authors.lastname: Yeo
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Eu Han
authors.initials: EH
authors.lastname: Lee
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hendrickson
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA asobeck@umn.edu sobeck.alex@gmail.com.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Sobeck
mesh_terms: D016590:Aphidicolin / Q000494:pharmacology; D019313:BRCA1 Protein / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004706:Endodeoxyribonucleases; D005199:Fanconi Anemia / Q000235:genetics* / Q000378:metabolism; D052236:Fanconi Anemia Complementation Group D2 Protein / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D000076228:MRE11 Homologue Protein; D009687:Nuclear Proteins / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D002352:Carrier Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; C499905:FANCD2 protein, human; D052236:Fanconi Anemia Complementation Group D2 Protein; C121766:MRE11 protein, human; D009687:Nuclear Proteins; D016590:Aphidicolin; D004706:Endodeoxyribonucleases; D000076228:MRE11 Homologue Protein; C410741:RBBP8 protein, human