title: Regulatory cross-talk determines the cellular levels of 53BP1 protein, a critical factor in DNA repair.
abstract: DNAdoublestrandbreaks (DSBs) severely disrupt DNA integrity. 53BP1 plays critical roles in determining DSB repair. Whereas the recruitment of 53BP1 to the DSB site is key for its function, recent evidence suggests that 53BP1's abundance also plays an important role in DSB repair because recruitment to damage sites will be influenced by protein availability. Initial evidence has pointed to three proteins, the ubiquitin-conjugating enzyme UbcH7, the cysteine protease cathepsin L (CTSL), and the nuclear structure protein lamin A/C, that may impact 53BP1 levels, but the roles of each protein and any interplay between them were unclear. Here we report that UbcH7-dependent degradation plays a major role in controlling 53BP1 levels both under normal growth conditions and during DNA damage. CTSL influenced 53BP1 degradation during DNA damage while having little effect under normal growth conditions. Interestingly, both the protein and the mRNA levels of CTSL were reduced in UbcH7-depleted cells. Lamin A/C interacted with 53BP1 under normal conditions. DNA damage disrupted the lamin A/C-53BP1 interaction, which preceded the degradation of 53BP1 in soluble, but not chromatin-enriched, cellular fractions. Inhibition of 53BP1 degradation by a proteasome inhibitor or by UbcH7 depletion restored the 53BP1-lamin A/C interaction. Depletion of lamin A/C, but not CTSL, caused a similar enhancement in cell sensitivity to DNA damage as UbcH7 depletion. These data suggest that multiple pathways collectively fine-tune the cellular levels of 53BP1 protein to ensure proper DSB repair and cell survival.
authors.affiliation: From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and.
authors.forename: Franklin
authors.initials: F
authors.lastname: Mayca Pozo
authors.affiliation: From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and.|Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, Guangzhou 510632, China.
authors.forename: Jinshan
authors.initials: J
authors.lastname: Tang
authors.affiliation: From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and.
authors.forename: Kristen W
authors.initials: KW
authors.lastname: Bonk
authors.affiliation: From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and.
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Keri
authors.affiliation: Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, Guangzhou 510632, China.
authors.forename: Xinsheng
authors.initials: X
authors.lastname: Yao
authors.affiliation: From the Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and yxz169@case.edu.
authors.forename: Youwei
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000072283:A549 Cells; D056668:Cathepsin L / Q000235:genetics / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D034904:Lamin Type A / Q000235:genetics / Q000378:metabolism; D000071857:Tumor Suppressor p53-Binding Protein 1 / Q000235:genetics / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism
chemical_list: C494847:LMNA protein, human; D034904:Lamin Type A; C498301:TP53BP1 protein, human; D000071857:Tumor Suppressor p53-Binding Protein 1; C079437:UBE2L3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; C534281:CTSL protein, human; D056668:Cathepsin L
keywords: DNA damage; DNA damage response; DNA repair; cell signaling; checkpoint control; degradation