title: HP1 regulates the localization of FANCJ at sites of DNA double-strand breaks.
abstract: The breast and ovarian cancer predisposition protein BRCA1 forms three mutually exclusive complexes with Fanconi anemia group J protein (FANCJ, also called BACH1 or BRIP1), CtIP, and Abraxas/RAP80 through its BRCA1 C terminus (BRCT) domains, while its RING domain binds to BRCA1-associated RING domain 1 (BARD1). We recently found that the interaction between heterochromatin protein 1 (HP1) and BARD1 is required for the accumulation of BRCA1 and CtIP at sites of DNA double-strand breaks. Here, we investigated the importance of HP1 and BARD1-HP1 interaction in the localization of FANCJ together with the other BRCA1-BRCT binding proteins to clarify the separate role of the HP1-mediated pathway from the RNF8/RNF168-induced ubiquitin-mediated pathway for BRCA1 function. FANCJ interacts with HP1γ in a BARD1-dependent manner, and this interaction was enhanced by ionizing radiation or irinotecan hydrochloride treatment. Simultaneous depletion of all three HP1 isoforms with shRNAs disrupts the accumulation of FANCJ and CtIP, but not RAP80, at double-strand break sites. Replacement of endogenous BARD1 with a mutant BARD1 that is incapable of binding to HP1 also disrupts the accumulation of FANCJ and CtIP, but not RAP80. In contrast, RNF168 depletion disrupts the accumulation of only RAP80, but not FANCJ or CtIP. Consequently, the accumulation of conjugated ubiquitin was only inhibited by RNF168 depletion, whereas the accumulation of RAD51 and sister chromatid exchange were only inhibited by HP1 depletion or disruption of the BARD1-HP1 interaction. Taken together, the results suggest that the BRCA1-FANCJ and BRCA1-CtIP complexes are not downstream of the RNF8/RNF168/ubiquitin pathway, but are instead regulated by the HP1 pathway that precedes homologous recombination DNA repair.
authors.affiliation: Department of Translational Oncology, St. Marianna University Graduate School of Medicine, Kawasaki, Japan.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Wu
authors.affiliation: Department of Translational Oncology, St. Marianna University Graduate School of Medicine, Kawasaki, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Togashi
authors.affiliation: Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Johmura
authors.affiliation: Division of Breast and Endocrine Surgery, Department of Surgery, Hyogo College of Medicine, Hyogo, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Miyoshi
authors.affiliation: Laboratory Medicine, St. Marianna University Graduate School of Medicine, Kawasaki, Japan.
authors.forename: Sachihiko
authors.initials: S
authors.lastname: Nobuoka
authors.affiliation: Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan.|Division of Cancer Cell Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakanishi
authors.affiliation: Department of Translational Oncology, St. Marianna University Graduate School of Medicine, Kawasaki, Japan. to@marianna-u.ac.jp.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Ohta
mesh_terms: D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins; D004706:Endodeoxyribonucleases; D051856:Fanconi Anemia Complementation Group Proteins / Q000378:metabolism*; D006367:HeLa Cells; D056488:Histone Chaperones; D006801:Humans; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D051135:Rad51 Recombinase / Q000378:metabolism; D012854:Sister Chromatid Exchange; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: C102108:BACH1 protein, human; D050976:Basic-Leucine Zipper Transcription Factors; D002352:Carrier Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D051856:Fanconi Anemia Complementation Group Proteins; D056488:Histone Chaperones; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; C466234:UIMC1 protein, human; D025801:Ubiquitin; D000090266:Chromobox Protein Homolog 5; C102449:BARD1 protein, human; C535210:RNF168 protein, human; D044767:Ubiquitin-Protein Ligases; D051135:Rad51 Recombinase; D004706:Endodeoxyribonucleases; C410741:RBBP8 protein, human
keywords: 
  FANCJ
  ; BRCA1; CtIP; DNA damage response; HP1