Fanconi Anemia Proteins FANCA, FANCC, and FANCG/XRCC9 Interact in a Functional Nuclear Complex

Abstract

Fanconi anemia (FA) is an autosomal recessive cancer susceptibility syndrome with at least eight complementation groups (A to H). Three FA genes, corresponding to complementation groups A, C, and G, have been cloned, but their cellular function remains unknown. We have previously demonstrated that the FANCA and FANCC proteins interact and form a nuclear complex in normal cells, suggesting that the proteins cooperate in a nuclear function. In this report, we demonstrate that the recently cloned FANCG/XRCC9 protein is required for binding of the FANCA and FANCC proteins. Moreover, the FANCG protein is a component of a nuclear protein complex containing FANCA and FANCC. The amino-terminal region of the FANCA protein is required for FANCG binding, FANCC binding, nuclear localization, and functional activity of the complex. Our results demonstrate that the three cloned FA proteins cooperate in a large multisubunit complex. Disruption of this complex results in the specific cellular and clinical phenotype common to most FA complementation groups.

ACKNOWLEDGMENTS

We thank C. Mathew for the BD32 (FA-A) cell line and H. Joenje for EUFA143 and EUFA316 cells.

This research was supported by NIH grants R01-HL5725 and PO1-CA39542. I.G.H. is supported by a fellowship from the Cancer Research Institute. A.D.D. is a Scholar of the Leukemia Society of America.