Phosphorylation of fanconi anemia (FA) complementation group G protein, FANCG, at serine 7 is important for function of the FA pathway.
Fanconi anemia (FA) is an autosomal recessive disease of cancer susceptibility. FA cells exhibit a characteristic hypersensitivity to DNA cross-linking agents. The molecular mechanism for the disease is unknown as few of the FA proteins have functional motifs. Several post-translational modifications of the proteins have been described. We and others have reported that the FANCG protein (Fanconi complementation group G) is phosphorylated. We show that in an in vitro kinase reaction FANCG is radioactively labeled. Mass spectrometry analysis detected a peptide containing phosphorylation of serine 7. Using PCR-mediated site-directed mutagenesis we mutated serine 7 to alanine. Only wild-type FANCG cDNA fully corrected FA-G mutant cells. We also tested the effect of human wild-type FANCG in Chinese hamster ovary cells in which the FANCG homologue is mutant. Human FANCG complemented these cells, whereas human FANCG(S7A) did not. Unexpectedly, FANCG(S7A) bound to and stabilized the endogenous forms of the FANCA and FANCC proteins in the FA-G cells. FANCG(S7A) aberrantly localized to globules in chromatin and did not abrogate the internuclear bridges seen in the FA-G mutant cells. Phosphorylation of serine 7 in FANCG is functionally important in the FA pathway.
Departments of Microbiology and Pediatrics, University of Virginia Health System, Charlottesville, Virginia 22908, USA.
Fengyu
F
Qiao
Jun
J
Mi
James B
JB
Wilson
Gang
G
Zhi
Natalie R
NR
Bucheimer
Nigel J
NJ
Jones
Gary M
GM
Kupfer
D000818:Animals; D016466:CHO Cells; D002843:Chromatin / Q000737:chemistry; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D052217:Fanconi Anemia Complementation Group A Protein; D052236:Fanconi Anemia Complementation Group D2 Protein; D052241:Fanconi Anemia Complementation Group G Protein; D006367:HeLa Cells; D006801:Humans; D016685:Mitomycin / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
D002843:Chromatin; D004268:DNA-Binding Proteins; C498471:FANCA protein, human; C499905:FANCD2 protein, human; C499909:FANCG protein, human; D052217:Fanconi Anemia Complementation Group A Protein; D052236:Fanconi Anemia Complementation Group D2 Protein; D052241:Fanconi Anemia Complementation Group G Protein; D009687:Nuclear Proteins; D025801:Ubiquitin; D012694:Serine; D016685:Mitomycin