Coordinate nuclear targeting of the FANCD2 and FANCI proteins via a FANCD2 nuclear localization signal

• Published in: PloS one Vol. 8; no. 11; p. e81387
• Main Authors: Boisvert, Rebecca A, Rego, Meghan A, Azzinaro, Paul A, Mauro, Maurizio, Howlett, Niall G
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 21.11.2013; Public Library of Science (PLoS)
• Subjects: Amino Acid Sequence; Amino acids; Anemia; Animals; Birth defects; Bone cancer; Bone marrow; Breast cancer; Cancer; Cell Line; Cell Nucleus - metabolism; Chromatin; Chromatin - metabolism; Congenital defects; Conserved Sequence; Crosslinking; Defects; Deoxyribonucleic acid; Disease susceptibility; DNA; DNA Damage; DNA repair; FANCD2 protein; Fanconi Anemia - genetics; Fanconi Anemia - metabolism; Fanconi Anemia Complementation Group D2 Protein - chemistry; Fanconi Anemia Complementation Group D2 Protein - genetics; Fanconi Anemia Complementation Group D2 Protein - metabolism; Fanconi Anemia Complementation Group Proteins - metabolism; Fanconi syndrome; Fanconi's anemia; Genes; Genetic aspects; Humans; Localization; Models, Biological; Molecular biology; Molecular Sequence Data; Mutants; Mutation; Nuclear Localization Signals - chemistry; Nuclear Localization Signals - genetics; Nuclear transport; Protein Transport; Proteins; Repair; Sequence Alignment; Structure-function relationships; Ubiquitination; Womens health; Rhode Island
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0081387

Fanconi anemia (FA) is a rare recessive disease, characterized by congenital defects, bone marrow failure, and increased cancer susceptibility. FA is caused by biallelic mutation of any one of sixteen genes. The protein products of these genes function cooperatively in the FA-BRCA pathway to repair DNA interstrand crosslinks (ICLs). A central step in the activation of this pathway is the monoubiquitination of the FANCD2 and FANCI proteins. Monoubiquitinated FANCD2 and FANCI localize to discrete chromatin regions where they function in ICL repair. Despite their critical role in ICL repair, very little is known about the structure, function, and regulation of the FANCD2 and FANCI proteins, or how they are targeted to the nucleus and chromatin. In this study, we describe the functional characterization of an amino-terminal FANCD2 nuclear localization signal (NLS). We demonstrate that the amino terminal 58 amino acids of FANCD2 can promote the nuclear expression of GFP and is necessary for the nuclear localization of FANCD2. Importantly, mutation of this FANCD2 NLS reveals that intact FANCD2 is required for the nuclear localization of a subset of FANCI. In addition, the NLS is necessary for the efficient monoubiquitination of FANCD2 and FANCI and, consequently, for their localization to chromatin. As a result, FANCD2 NLS mutants fail to rescue the ICL sensitivity of FA-D2 patient cells. Our studies yield important insight into the domain structure of the poorly characterized FANCD2 protein, and reveal a previously unknown mechanism for the coordinate nuclear import of a subset of FANCD2 and FANCI, a key early step in the cellular ICL response.