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Gaddameedhi S, Kemp MG, Reardon JT, Shields JM, Smith-Roe SL, Kaufmann WK, Sancar A. Similar nucleotide excision repair capacity in melanocytes and melanoma cells. Cancer Res 2010; 70:4922-30. [PMID: 20501836 DOI: 10.1158/0008-5472.can-10-0095] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Sunlight UV exposure produces DNA photoproducts in skin that are repaired solely by nucleotide excision repair in humans. A significant fraction of melanomas are thought to result from UV-induced DNA damage that escapes repair; however, little evidence is available about the functional capacity of normal human melanocytes, malignant melanoma cells, and metastatic melanoma cells to repair UV-induced photoproducts in DNA. In this study, we measured nucleotide excision repair in both normal melanocytes and a panel of melanoma cell lines. Our results show that in 11 of 12 melanoma cell lines tested, UV photoproduct repair occurred as efficiently as in primary melanocytes. Importantly, repair capacity was not affected by mutation in the N-RAS or B-RAF oncogenes, nor was a difference observed between a highly metastatic melanoma cell line (A375SM) or its parental line (A375P). Lastly, we found that although p53 status contributed to photoproduct removal efficiency, its role did not seem to be mediated by enhanced expression or activity of DNA binding protein DDB2. We concluded that melanoma cells retain capacity for nucleotide excision repair, the loss of which probably does not commonly contribute to melanoma progression.
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Affiliation(s)
- Shobhan Gaddameedhi
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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2
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Two-stage dynamic DNA quality check by xeroderma pigmentosum group C protein. EMBO J 2009; 28:2387-99. [PMID: 19609301 DOI: 10.1038/emboj.2009.187] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Accepted: 06/17/2009] [Indexed: 11/08/2022] Open
Abstract
Xeroderma pigmentosum group C (XPC) protein initiates the DNA excision repair of helix-distorting base lesions. To understand how this versatile subunit searches for aberrant sites within the vast background of normal genomic DNA, the real-time redistribution of fluorescent fusion constructs was monitored after high-resolution DNA damage induction. Bidirectional truncation analyses disclosed a surprisingly short recognition hotspot, comprising approximately 15% of human XPC, that includes two beta-hairpin domains with a preference for non-hydrogen-bonded bases in double-stranded DNA. However, to detect damaged sites in living cells, these DNA-attractive domains depend on the partially DNA-repulsive action of an adjacent beta-turn extension that promotes the mobility of XPC molecules searching for lesions. The key function of this dynamic interaction surface is shown by a site-directed charge inversion, which results in increased affinity for native DNA, retarded nuclear mobility and diminished repair efficiency. These studies reveal a two-stage discrimination process, whereby XPC protein first deploys a dynamic sensor interface to rapidly interrogate the double helix, thus forming a transient recognition intermediate before the final installation of a more static repair-initiating complex.
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Al Khateeb WM, Schroeder DF. Overexpression of Arabidopsis damaged DNA binding protein 1A (DDB1A) enhances UV tolerance. PLANT MOLECULAR BIOLOGY 2009; 70:371-83. [PMID: 19288212 DOI: 10.1007/s11103-009-9479-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Accepted: 02/27/2009] [Indexed: 05/19/2023]
Abstract
Damaged DNA Binding protein 1 (DDB1) is a conserved protein and a component of multiple cellular complexes. Arabidopsis has two homologues of DDB1: DDB1A and DDB1B. In this study we examine the role of DDB1A in Arabidopsis UV tolerance and DNA repair using a DDB1A null mutant (ddb1a) and overexpression lines. DDB1A overexpression lines showed higher levels of UV-resistance than wild-type in a range of assays as well as faster DNA repair. However a significant difference between wild-type plants and ddb1a mutants was only observed immediately following UV treatment in root length and photoproduct repair assays. DDB1A and DDB1B mRNA levels increased 3 h after UV exposure and DDB1A is required for UV regulation of DDB1B and DDB2 mRNA levels. In conclusion, while DDB1A is sufficient to increase Arabidopsis UV tolerance, it is only necessary for immediate response to UV damage.
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Affiliation(s)
- Wesam M Al Khateeb
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada.
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Itoh T, Iwashita S, Cohen MB, Meyerholz DK, Linn S. Ddb2 is a haploinsufficient tumor suppressor and controls spontaneous germ cell apoptosis. Hum Mol Genet 2007; 16:1578-86. [PMID: 17468495 DOI: 10.1093/hmg/ddm107] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Damage-specific DNA-binding (DDB) protein heterodimer has been extensively studied in the context of nucleotide excision repair. However, the smaller subunit, DDB2, is also implicated in tumor suppressor p53-mediated processes, although the precise details of the DDB2 - p53 interactions are unknown. Here, we report that Ddb2(-/-) and Ddb2(+/-) mice have shortened lifespans and increased frequency and spectrum of spontaneous tumors. Notably, Ddb2 deficiency enhances lung and mammary adenocarcinomas. Ddb2(-/-) mice are smaller than normal. Whereas weights of kidneys and livers are reduced proportionately, spleens from Ddb2(-/-) mice gradually enlarge with age due to lymphoid proliferation. Ddb2(-/-) mice also have larger testes, and the testicular germ cells show significantly decreased spontaneous apoptosis. These changes parallel reduced levels of p53 and its serine 15 phosphorylation in testicular germ cells. Since tumors that appeared in heterozygous Ddb2(+/-) mice conserve the wild-type Ddb2 allele, Ddb2 RNA expression and Ddb2 exon sequence, Ddb2 heterozygosity can facilitate tumor development as a haploinsufficient tumor suppressor. These results demonstrate that in whole animals as in cultured cells Ddb2 can regulate apoptosis and tumor incidence.
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Affiliation(s)
- Toshiki Itoh
- Department of Pathology, The University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA.
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Itoh T. Xeroderma pigmentosum group E and DDB2, a smaller subunit of damage-specific DNA binding protein: Proposed classification of xeroderma pigmentosum, Cockayne syndrome, and ultraviolet-sensitive syndrome. J Dermatol Sci 2006; 41:87-96. [PMID: 16325378 DOI: 10.1016/j.jdermsci.2005.10.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2005] [Accepted: 10/25/2005] [Indexed: 11/26/2022]
Abstract
Xeroderma pigmentosum is a rare photosensitive syndrome that comprises eight different genetic diseases (A to G; variant (V)). Although genotype-phenotype correlations have been evaluated in most XP groups, the relationship between the E subgroup of xeroderma pigmentosum (XP-E) and damage-specific DNA binding protein (DDB) still remained a mystery. Recent studies have provided new insight for XP-E and the role(s) of DDB2, a smaller subunit of DDB. Reclassification studies have confirmed that mutations in DDB2 give rise to XP-E. The mouse model of XP-E demonstrated that DDB2 was well conserved between mouse and human and was critical in controlling proper cell-survival through regulating the tumor suppressor p53-mediated responses after ultraviolet (UV)-irradiation: i.e. defective DDB2 causes the resistance to cell-killing by UV-irradiation due to decreased p53-mediated apoptosis. These phenotypes are unique to XP-E because other XP groups show normal (XP-V) or hypersensitivity (XP-A, B, C, D, F, and G) to UV-irradiation. Thus XP-E is defined as a skin cancer prone disease with unique resistance to UV-irradiation.
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Affiliation(s)
- Toshiki Itoh
- Department of Pathology, The University of Iowa, Carver College of Medicine, 200 Hawkins dr., Iowa City, IA 52242, USA.
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Sancar A, Lindsey-Boltz LA, Unsal-Kaçmaz K, Linn S. Molecular Mechanisms of Mammalian DNA Repair and the DNA Damage Checkpoints. Annu Rev Biochem 2004; 73:39-85. [PMID: 15189136 DOI: 10.1146/annurev.biochem.73.011303.073723] [Citation(s) in RCA: 2346] [Impact Index Per Article: 117.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
DNA damage is a relatively common event in the life of a cell and may lead to mutation, cancer, and cellular or organismic death. Damage to DNA induces several cellular responses that enable the cell either to eliminate or cope with the damage or to activate a programmed cell death process, presumably to eliminate cells with potentially catastrophic mutations. These DNA damage response reactions include: (a) removal of DNA damage and restoration of the continuity of the DNA duplex; (b) activation of a DNA damage checkpoint, which arrests cell cycle progression so as to allow for repair and prevention of the transmission of damaged or incompletely replicated chromosomes; (c) transcriptional response, which causes changes in the transcription profile that may be beneficial to the cell; and (d) apoptosis, which eliminates heavily damaged or seriously deregulated cells. DNA repair mechanisms include direct repair, base excision repair, nucleotide excision repair, double-strand break repair, and cross-link repair. The DNA damage checkpoints employ damage sensor proteins, such as ATM, ATR, the Rad17-RFC complex, and the 9-1-1 complex, to detect DNA damage and to initiate signal transduction cascades that employ Chk1 and Chk2 Ser/Thr kinases and Cdc25 phosphatases. The signal transducers activate p53 and inactivate cyclin-dependent kinases to inhibit cell cycle progression from G1 to S (the G1/S checkpoint), DNA replication (the intra-S checkpoint), or G2 to mitosis (the G2/M checkpoint). In this review the molecular mechanisms of DNA repair and the DNA damage checkpoints in mammalian cells are analyzed.
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Affiliation(s)
- Aziz Sancar
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7260, USA.
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Itoh T, Cado D, Kamide R, Linn S. DDB2 gene disruption leads to skin tumors and resistance to apoptosis after exposure to ultraviolet light but not a chemical carcinogen. Proc Natl Acad Sci U S A 2004; 101:2052-7. [PMID: 14769931 PMCID: PMC357050 DOI: 10.1073/pnas.0306551101] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Indexed: 11/18/2022] Open
Abstract
Mutations in the human DDB2 gene give rise to xeroderma pigmentosum group E, a disease characterized by increased skin tumorigenesis in response to UV-irradiation. Cell strains derived from xeroderma pigmentosum group E individuals also have enhanced resistance to UV-irradiation due to decreased p53-mediated apoptosis. To further address the precise function(s) of DDB2 and the consequence of non-naturally occurring DDB2 mutations, we generated mice with a disruption of the gene. The mice exhibited significantly enhanced skin carcinogenesis in response to UV-irradiation, and cells from the DDB2(-/-) mice were abnormally resistant to killing by the radiation and had diminished UV-induced, p53-mediated apoptosis. Notably, the cancer-prone phenotype and the resistance to cellular killing were not observed after exposure to the chemical carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA), to which mice carrying defective nucleotide excision repair genes respond with enhanced tumors and cell killing. Although cells from heterozygous DDB2(+/-) mice appeared normal, these mice had enhanced skin carcinogenesis after UV-irradiation, so that XP-E heterozygotes might be at risk for carcinogenesis. In sum, these results demonstrate that DDB2 is well conserved between humans and mice and functions as a tumor suppressor, at least in part, by controlling p53-mediated apoptosis after UV-irradiation.
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Affiliation(s)
- Toshiki Itoh
- Divisions of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA. toshiki@
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Itoh T, O'Shea C, Linn S. Impaired regulation of tumor suppressor p53 caused by mutations in the xeroderma pigmentosum DDB2 gene: mutual regulatory interactions between p48(DDB2) and p53. Mol Cell Biol 2003; 23:7540-53. [PMID: 14560002 PMCID: PMC207631 DOI: 10.1128/mcb.23.21.7540-7553.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Tumor suppressor p53 controls cell cycle progression and apoptosis following DNA damage, thus minimizing carcinogenesis. Mutations in the human DDB2 gene generate the E subgroup of xeroderma pigmentosum (XP-E). We report here that XP-E strains are defective in UV irradiation-induced apoptosis due to severely reduced basal and UV-induced p53 levels. These defects are restored by infection with a p53 cDNA expression construct or with a DDB2 expression construct if and only if it contains intron 4, which includes a nonmutated p53 consensus-binding site. We propose that both before and after UV irradiation, DDB2 directly regulates p53 levels, while DDB2 expression is itself regulated by p53.
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Affiliation(s)
- Toshiki Itoh
- Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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Zolezzi F, Fuss J, Uzawa S, Linn S. Characterization of a Schizosaccharomyces pombe strain deleted for a sequence homologue of the human damaged DNA binding 1 (DDB1) gene. J Biol Chem 2002; 277:41183-91. [PMID: 12181326 DOI: 10.1074/jbc.m207890200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human damaged DNA-binding protein (DDB) is a heterodimer of p48/DDB2 and p127/DDB1 subunits. Mutations in DDB2 are responsible for Xeroderma Pigmentosum group E, but no mutants of mammalian DDB1 have been described. To study DDB1, the Schizosaccharomyces pombe DDB1 sequence homologue (ddb1(+)) was cloned, and a ddb1 deletion strain was constructed. The gene is not essential; however, mutant cells showed a 37% impairment in colony-forming ability, an elongated phenotype, and abnormal nuclei. The ddb1Delta strain was sensitive to UV irradiation, X-rays, methylmethane sulfonate, and thiabendazole, and these sensitivities were compared with those of the well characterized rad13Delta, rhp51Delta, and cds1Delta mutant strains. Ddb1p showed nuclear and nucleolar localization, and the aberrant nuclear structures observed in the ddb1Delta strain suggest a role for Ddb1p in chromosome segregation.
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Affiliation(s)
- Francesca Zolezzi
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3206, USA
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Abstract
UV-damaged DNA-binding protein (UV-DDB) is composed of two subunits, DDB1 (p127) and DDB2 (p48). Mutations in the DDB2 gene inactivate UV-DDB in individuals from complementation group E of xeroderma pigmentosum (XP-E), an autosomal recessive disease characterized by sun sensitivity, severe risk for skin cancer and defective nucleotide excision repair. UV-DDB is also deficient in many rodent tissues, exposing a shortcoming in rodent models for cancer. In vitro, UV-DDB binds to cyclobutane pyrimidine dimers (CPDs), 6-4 photoproducts and other DNA lesions, stimulating the excision of CPDs, and to a lesser extent, of 6-4 photoproducts. In vivo, UV-DDB plays an important role in the p53-dependent response of mammalian cells to DNA damage. When cells are exposed to UV, the resulting accumulation of p53 activates DDB2 transcription, which leads to increased levels of UV-DDB. Binding of UV-DDB to CPDs targets these lesions for global genomic repair, suppressing mutations without affecting UV survival. Apparently, cells are able to survive with unrepaired CPDs because of the activity of bypass DNA polymerases. Finally, there is evidence that UV-DDB may have roles in the cell that are distinct from DNA repair.
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Affiliation(s)
- Jean Tang
- Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305-5151, USA
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