title: DDB2 decides cell fate following DNA damage.
abstract: The xeroderma pigmentosum complementation group E (XP-E) gene product damaged-DNA binding protein 2 (DDB2) plays important roles in nucleotide excision repair (NER). Previously, we showed that DDB2 participates in NER by regulating the level of p21(Waf1/Cip1). Here we show that the p21(Waf1/Cip1) -regulatory function of DDB2 plays a central role in defining the response (apoptosis or arrest) to DNA damage. The DDB2-deficient cells are resistant to apoptosis in response to a variety of DNA-damaging agents, despite activation of p53 and the pro-apoptotic genes. Instead, these cells undergo cell cycle arrest. Also, the DDB2-deficient cells are resistant to E2F1-induced apoptosis. The resistance to apoptosis of the DDB2-deficient cells is caused by an increased accumulation of p21(Waf1/Cip1) after DNA damage. We provide evidence that DDB2 targets p21(Waf1/Cip1) for proteolysis. The resistance to apoptosis in DDB2-deficient cells also involves Mdm2 in a manner that is distinct from the p53-regulatory activity of Mdm2. Our results provide evidence for a new regulatory loop involving the NER protein DDB2, Mdm2, and p21(Waf1/Cip1) that is critical in deciding cell fate (apoptosis or arrest) upon DNA damage.
authors.affiliation: Department of Biochemistry and Molecular Genetics (M/C 669), Cancer Center, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, IL 60607, USA.
authors.forename: Tanya
authors.initials: T
authors.lastname: Stoyanova
authors.forename: Nilotpal
authors.initials: N
authors.lastname: Roy
authors.forename: Dragana
authors.initials: D
authors.lastname: Kopanja
authors.forename: Srilata
authors.initials: S
authors.lastname: Bagchi
authors.forename: Pradip
authors.initials: P
authors.lastname: Raychaudhuri
mesh_terms: D015250:Aclarubicin / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D002478:Cells, Cultured; D002945:Cisplatin / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000502:physiology*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D018345:Mice, Knockout; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; C117669:DDB2 protein, human; D004268:DNA-Binding Proteins; C496850:Ddb2 protein, mouse; D016159:Tumor Suppressor Protein p53; D015250:Aclarubicin; D051736:Proto-Oncogene Proteins c-mdm2; D002945:Cisplatin