FANCG promotes formation of a newly identified protein complex containing BRCA2, FANCD2 and XRCC3.
Fanconi anemia (FA) is a human disorder characterized by cancer susceptibility and cellular sensitivity to DNA crosslinks and other damages. Thirteen complementation groups and genes are identified, including BRCA2, which is defective in the FA-D1 group. Eight of the FA proteins, including FANCG, participate in a nuclear core complex that is required for the monoubiquitylation of FANCD2 and FANCI. FANCD2, like FANCD1/BRCA2, is not part of the core complex, and we previously showed direct BRCA2-FANCD2 interaction using yeast two-hybrid analysis. We now show in human and hamster cells that expression of FANCG protein, but not the other core complex proteins, is required for co-precipitation of BRCA2 and FANCD2. We also show that phosphorylation of FANCG serine 7 is required for its co-precipitation with BRCA2, XRCC3 and FANCD2, as well as the direct interaction of BRCA2-FANCD2. These results argue that FANCG has a role independent of the FA core complex, and we propose that phosphorylation of serine 7 is the signalling event required for forming a discrete complex comprising FANCD1/BRCA2-FANCD2-FANCG-XRCC3 (D1-D2-G-X3). Cells that fail to express either phospho-Ser7-FANCG, or full length BRCA2 protein, lack the interactions amongst the four component proteins. A role for D1-D2-G-X3 in homologous recombination repair (HRR) is supported by our finding that FANCG and the RAD51-paralog XRCC3 are epistatic for sensitivity to DNA crosslinking compounds in DT40 chicken cells. Our findings further define the intricate interface between FANC and HRR proteins in maintaining chromosome stability.
Wilson
J B
JB
Molecular Oncology and Stem Cell Research Group, School of Biological Sciences, University of Liverpool, Liverpool, UK.
Yamamoto
K
K
Marriott
A S
AS
Hussain
S
S
Sung
P
P
Hoatlin
M E
ME
Mathew
C G
CG
Takata
M
M
Thompson
L H
LH
Kupfer
G M
GM
Jones
N J
NJ
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D024682:BRCA2 Protein / Q000378:metabolism*; D016466:CHO Cells; D018797:Cell Cycle Proteins / Q000502:physiology; D002645:Chickens; D043171:Chromosomal Instability; D006224:Cricetinae; D003412:Cricetulus; D004268:DNA-Binding Proteins / Q000378:metabolism*; D052217:Fanconi Anemia Complementation Group A Protein / Q000378:metabolism; D052236:Fanconi Anemia Complementation Group D2 Protein / Q000378:metabolism*; D052219:Fanconi Anemia Complementation Group F Protein / Q000378:metabolism; D052241:Fanconi Anemia Complementation Group G Protein / Q000502:physiology*; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011995:Recombination, Genetic; D012694:Serine / Q000378:metabolism
D024682:BRCA2 Protein; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C498471:FANCA protein, human; C499905:FANCD2 protein, human; C499901:FANCF protein, human; C499909:FANCG protein, human; D052217:Fanconi Anemia Complementation Group A Protein; D052236:Fanconi Anemia Complementation Group D2 Protein; D052219:Fanconi Anemia Complementation Group F Protein; D052241:Fanconi Anemia Complementation Group G Protein; C110901:X-ray repair cross complementing protein 3; D012694:Serine; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases