title: Fanconi anemia proteins FANCD2 and FANCI exhibit different DNA damage responses during S-phase.
abstract: Fanconi anemia (FA) pathway members, FANCD2 and FANCI, contribute to the repair of replication-stalling DNA lesions. FA pathway activation relies on phosphorylation of FANCI by the ataxia telangiectasia and Rad3-related (ATR) kinase, followed by monoubiquitination of FANCD2 and FANCI by the FA core complex. FANCD2 and FANCI are thought to form a functional heterodimer during DNA repair, but it is unclear how dimer formation is regulated or what the functions of the FANCD2-FANCI complex versus the monomeric proteins are. We show that the FANCD2-FANCI complex forms independently of ATR and FA core complex, and represents the inactive form of both proteins. DNA damage-induced FA pathway activation triggers dissociation of FANCD2 from FANCI. Dissociation coincides with FANCD2 monoubiquitination, which significantly precedes monoubiquitination of FANCI; moreover, monoubiquitination responses of FANCD2 and FANCI exhibit distinct DNA substrate specificities. A phosphodead FANCI mutant fails to dissociate from FANCD2, whereas phosphomimetic FANCI cannot interact with FANCD2, indicating that FANCI phosphorylation is the molecular trigger for FANCD2-FANCI dissociation. Following dissociation, FANCD2 binds replicating chromatin prior to-and independently of-FANCI. Moreover, the concentration of chromatin-bound FANCD2 exceeds that of FANCI throughout replication. Our results suggest that FANCD2 and FANCI function separately at consecutive steps during DNA repair in S-phase.
authors: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
authors: Archana
authors: A
authors: Sareen
authors: Indrajit
authors: I
authors: Chaudhury
authors: Nicole
authors: N
authors: Adams
authors: Alexandra
authors: A
authors: Sobeck
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002843:Chromatin / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D052236:Fanconi Anemia Complementation Group D2 Protein / Q000378:metabolism*; D051856:Fanconi Anemia Complementation Group Proteins / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D016196:S Phase / Q000235:genetics*; D054875:Ubiquitination; D029867:Xenopus Proteins / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; C576817:FANCD2 protein, Xenopus; C546473:FANCI Protein, Xenopus; D052236:Fanconi Anemia Complementation Group D2 Protein; D051856:Fanconi Anemia Complementation Group Proteins; D029867:Xenopus Proteins; C576898:Atr protein, Xenopus; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases