RNF4-mediated polyubiquitination regulates the Fanconi anemia/BRCA pathway.
The Fanconi anemia/BRCA (FA/BRCA) pathway is a DNA repair pathway that is required for excision of DNA interstrand cross-links. The 17 known FA proteins, along with several FA-associated proteins (FAAPs), cooperate in this pathway to detect, unhook, and excise DNA cross-links and to subsequently repair the double-strand breaks generated in the process. In the current study, we identified a patient with FA with a point mutation in FANCA, which encodes a mutant FANCA protein (FANCAI939S). FANCAI939S failed to bind to the FAAP20 subunit of the FA core complex, leading to decreased stability. Loss of FAAP20 binding exposed a SUMOylation site on FANCA at amino acid residue K921, resulting in E2 SUMO-conjugating enzyme UBC9-mediated SUMOylation, RING finger protein 4-mediated (RNF4-mediated) polyubiquitination, and proteasome-mediated degradation of FANCA. Mutation of the SUMOylation site of FANCA rescued the expression of the mutant protein. Wild-type FANCA was also subject to SUMOylation, RNF4-mediated polyubiquitination, and degradation, suggesting that regulated release of FAAP20 from FANCA is a critical step in the normal FA pathway. Consistent with this model, cells lacking RNF4 exhibited interstrand cross-linker hypersensitivity, and the gene encoding RNF4 was epistatic with the other genes encoding members of the FA/BRCA pathway. Together, the results from our study underscore the importance of analyzing unique patient-derived mutations for dissecting complex DNA repair processes.
Jenny
J
Xie
Hyungjin
H
Kim
Lisa A
LA
Moreau
Shannon
S
Puhalla
Judy
J
Garber
Muthana
M
Al Abo
Shunichi
S
Takeda
Alan D
AD
D'Andrea
D000328:Adult; D019313:BRCA1 Protein / Q000502:physiology*; D045744:Cell Line, Tumor; D004260:DNA Repair / Q000235:genetics / Q000502:physiology*; D005199:Fanconi Anemia / Q000235:genetics*; D052217:Fanconi Anemia Complementation Group A Protein / Q000235:genetics / Q000502:physiology*; D051856:Fanconi Anemia Complementation Group Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D005260:Female; D019398:Genes, BRCA1; D006801:Humans; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000502:physiology*; D010375:Pedigree; D010641:Phenotype; D017354:Point Mutation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational / Q000502:physiology; D059748:Proteolysis; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D058207:Sumoylation; D014157:Transcription Factors / Q000502:physiology*; D064726:Triple Negative Breast Neoplasms / Q000235:genetics; D054875:Ubiquitination / Q000502:physiology
D019313:BRCA1 Protein; C492913:BRCA1 protein, human; C570807:FAAP20 protein, human; C498471:FANCA protein, human; D052217:Fanconi Anemia Complementation Group A Protein; D051856:Fanconi Anemia Complementation Group Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C114070:RNF4 protein, human; D014157:Transcription Factors; D046988:Proteasome Endopeptidase Complex