A novel ubiquitin ligase is deficient in Fanconi anemia


Fanconi anemia is a recessively inherited disease characterized by congenital defects, bone marrow failure and cancer susceptibility1,2. Cells from individuals with Fanconi anemia are highly sensitive to DNA-crosslinking drugs, such as mitomycin C (MMC). Fanconi anemia proteins function in a DNA damage response pathway involving breast cancer susceptibility gene products, BRCA1 and BRCA2 (refs. 1,2). A key step in this pathway is monoubiquitination of FANCD2, resulting in the redistribution of FANCD2 to nuclear foci containing BRCA1 (ref. 3). The underlying mechanism is unclear because the five Fanconi anemia proteins known to be required for this ubiquitination have no recognizable ubiquitin ligase motifs. Here we report a new component of a Fanconi anemia protein complex, called PHF9, which possesses E3 ubiquitin ligase activity in vitro and is essential for FANCD2 monoubiquitination in vivo. Because PHF9 is defective in a cell line derived from an individual with Fanconi anemia, we conclude that PHF9 (also called FANCL) represents a novel Fanconi anemia complementation group (FA-L). Our data suggest that PHF9 has a crucial role in the Fanconi anemia pathway as the likely catalytic subunit required for monoubiquitination of FANCD2.

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Figure 1: PHF9 is a component of the Fanconi anemia core complex.
Figure 3: PHF9/Pog contains a PHD finger–type E3 ubiquitin ligase motif and has autoubiquitin ligase activity in vitro.
Figure 2: Nuclear localization of PHF9 is defective in cells from several Fanconi anemia complementation groups.
Figure 4: PHF9-knockdown cells have less monoubiquitinated FANCD2 and fewer FANCD2 nuclear foci.
Figure 5: PHF9 is deficient in an individual with Fanconi anemia.

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We thank K. J. Patel for FANCE antibody and communicating unpublished data, M. Grompe for FANCD2 cDNA, Z. Lu and T. Hunter for MEKK1, Y. Qiong for ubiquitin vectors, J. Chen for BRCA1 cells, Y. Yang for ubiquitin reagents, N. Sherman for mass spectrometry identification, J. Qin and L. Li for advice, D. Schlessinger for critical reading of the manuscript and the National Cell Culture Center for providing cells. W.W. has received funding from the Ellison Medical Foundation and Rett Syndrome Research Foundation. This work was also supported by the Dutch Cancer Society (A.L.M. and H.J.V.), the Netherlands Organization for Health Research and Development (J.P.W. and Q.W.) and the US National Institutes of Health (W.W. and M.E.H.).

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Correspondence to Weidong Wang.

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Meetei, A., de Winter, J., Medhurst, A. et al. A novel ubiquitin ligase is deficient in Fanconi anemia. Nat Genet 35, 165–170 (2003). https://doi.org/10.1038/ng1241

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