Heterogeneous activation of the Fanconi anemia pathway by patient-derived FANCA mutants.
Fanconi anemia (FA) is an autosomal recessive disorder of hematopoiesis characterized by hypersensitivity to DNA crosslinkers such as mitomycin C (MMC). There is growing evidence for a model of the FA pathway, wherein a nuclear multiprotein complex of five FA proteins (FANCA, C, E, F and G) regulates activation of FANCD2 into a monoubiquitinated form, which, collaborating with the BRCA1 machinery, affects cellular response to DNA damage. However, the role of the FA pathway in defective DNA damage response caused by various mutant forms of FA proteins has not been fully assessed. In the present study, 21 patient-derived FANCA mutants with a missense or a small in-frame deletion were expressed in FANCA-deficient fibroblasts and examined for complementation of MMC sensitivity and for reconstitution of the FA pathway: FANCA phosphorylation, interaction with FANCC, FANCF and FANCG and nuclear localization and FANCD2 monoubiquitination. The altered FANCA proteins complemented MMC sensitivity at different grades: five proteins (group I) behaved like wild-type FANCA, whereas the other proteins were either mildly (group II, n=4) or severely (group III, n=12) impaired. Group I proteins showed an apparently normal reconstitution of the FA pathway, thus they may be pathogenic by reducing endogenous expression or possibly benign polymorphisms. Reconstitution of the FA pathway by group II and III mutants closely correlated with cellular sensitivity to MMC. The different activation of the FA pathway may partly account for the phenotypic variation seen in FA patients.
Adachi
Daiki
D
Division of Genetic Diagnosis, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Oda
Tsukasa
T
Yagasaki
Hiroshi
H
Nakasato
Keiko
K
Taniguchi
Toshiyasu
T
D'Andrea
Alan D
AD
Asano
Shigetaka
S
Yamashita
Takayuki
T
D019943:Amino Acid Substitution / Q000235:genetics; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D005199:Fanconi Anemia / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology*; D052217:Fanconi Anemia Complementation Group A Protein; D052218:Fanconi Anemia Complementation Group C Protein; D052236:Fanconi Anemia Complementation Group D2 Protein; D052239:Fanconi Anemia Complementation Group E Protein; D052219:Fanconi Anemia Complementation Group F Protein; D052241:Fanconi Anemia Complementation Group G Protein; D051856:Fanconi Anemia Complementation Group Proteins; D005347:Fibroblasts / Q000737:chemistry / Q000378:metabolism / Q000473:pathology / Q000821:virology; D005816:Genetic Complementation Test; D006801:Humans; D020125:Mutation, Missense / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011506:Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C498471:FANCA protein, human; C497651:FANCC protein, human; C499905:FANCD2 protein, human; C499907:FANCE protein, human; C499901:FANCF protein, human; C499909:FANCG protein, human; D052217:Fanconi Anemia Complementation Group A Protein; D052218:Fanconi Anemia Complementation Group C Protein; D052236:Fanconi Anemia Complementation Group D2 Protein; D052239:Fanconi Anemia Complementation Group E Protein; D052219:Fanconi Anemia Complementation Group F Protein; D052241:Fanconi Anemia Complementation Group G Protein; D051856:Fanconi Anemia Complementation Group Proteins; D009687:Nuclear Proteins; D011506:Proteins; D016601:RNA-Binding Proteins