title: DDB1 maintains genome integrity through regulation of Cdt1.
abstract: DDB1, a component of a Cul4A ubiquitin ligase complex, promotes nucleotide excision repair (NER) and regulates DNA replication. We have investigated the role of human DDB1 in maintaining genome stability. DDB1-depleted cells accumulate DNA double-strand breaks in widely dispersed regions throughout the genome and have activated ATM and ATR cell cycle checkpoints. Depletion of Cul4A yields similar phenotypes, indicating that an E3 ligase function of DDB1 is important for genome maintenance. In contrast, depletion of DDB2, XPA, or XPC does not cause activation of DNA damage checkpoints, indicating that defects in NER are not involved. One substrate of DDB1-Cul4A that is crucial for preventing genome instability is Cdt1. DDB1-depleted cells exhibit increased levels of Cdt1 protein and rereplication, despite containing other Cdt1 regulatory mechanisms. The rereplication, accumulation of DNA damage, and activation of checkpoint responses in DDB1-depleted cells require entry into S phase and are partially, but not completely, suppressed by codepletion of Cdt1. Therefore, DDB1 prevents DNA lesions from accumulating in replicating human cells, in part by regulating Cdt1 degradation.
authors.affiliation: Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA.
authors.forename: Courtney A
authors.initials: CA
authors.lastname: Lovejoy
authors.forename: Kimberli
authors.initials: K
authors.lastname: Lock
authors.forename: Ashwini
authors.initials: A
authors.lastname: Yenamandra
authors.forename: David
authors.initials: D
authors.lastname: Cortez
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002877:Chromosomes, Human; D044842:Cullin Proteins / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018816:Genes, cdc; D015894:Genome, Human; D042822:Genomic Instability; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D014983:Xeroderma Pigmentosum; D051760:Xeroderma Pigmentosum Group A Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C467199:CDT1 protein, human; C114234:CUL4A protein, human; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D021122:Protein Subunits; D034741:RNA, Small Interfering; D044786:S-Phase Kinase-Associated Proteins; D025521:Tumor Suppressor Proteins; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; C086984:XPC protein, human; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases