51
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Zhu M, Weiss RS. Increased common fragile site expression, cell proliferation defects, and apoptosis following conditional inactivation of mouse Hus1 in primary cultured cells. Mol Biol Cell 2007; 18:1044-55. [PMID: 17215515 PMCID: PMC1805091 DOI: 10.1091/mbc.e06-10-0957] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Targeted disruption of the mouse Hus1 cell cycle checkpoint gene results in embryonic lethality and proliferative arrest in cultured cells. To investigate the essential functions of Hus1, we developed a system for the regulated inactivation of mouse Hus1 in primary fibroblasts. Inactivation of a loxP site-flanked conditional Hus1 allele by using a cre-expressing adenovirus resulted in reduced cell doubling, cell cycle alterations, and increased apoptosis. These phenotypes were associated with a significantly increased frequency of gross chromosomal abnormalities and an S-phase-specific accumulation of phosphorylated histone H2AX, an indicator of double-stranded DNA breaks. To determine whether these chromosomal abnormalities occurred randomly or at specific genomic regions, we assessed the stability of common fragile sites, chromosomal loci that are prone to breakage in cells undergoing replication stress. Hus1 was found to be essential for fragile site stability, because spontaneous chromosomal abnormalities occurred preferentially at common fragile sites upon conditional Hus1 inactivation. Although p53 levels increased after Hus1 loss, deletion of p53 failed to rescue the cell-doubling defect or increased apoptosis in conditional Hus1 knockout cells. In summary, we propose that Hus1 loss leads to chromosomal instability during DNA replication, triggering increased apoptosis and impaired proliferation through p53-independent mechanisms.
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Affiliation(s)
- Min Zhu
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853
| | - Robert S. Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853
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52
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Ruike T, Takeuchi R, Takata KI, Oshige M, Kasai N, Shimanouchi K, Kanai Y, Nakamura R, Sugawara F, Sakaguchi K. Characterization of a second proliferating cell nuclear antigen (PCNA2) from Drosophila melanogaster. FEBS J 2007; 273:5062-73. [PMID: 17087725 DOI: 10.1111/j.1742-4658.2006.05504.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The eukaryotic DNA polymerase processivity factor, proliferating cell nuclear antigen, is an essential component in the DNA replication and repair machinery. In Drosophila melanogaster, we cloned a second PCNA cDNA that differs from that encoded by the gene mus209 (for convenience called DmPCNA1 in this article). The second PCNA cDNA (DmPCNA2) encoded a 255 amino acid protein with 51.7% identity to DmPCNA1, and was ubiquitously expressed during Drosophila development. DmPCNA2 was localized in nuclei as a homotrimeric complex and associated with Drosophila DNA polymerase delta and epsilonin vivo. Treatment of cells with methyl methanesulfonate or hydrogen peroxide increased the amount of both DmPCNA2 and DmPCNA1 associating with chromatin, whereas exposure to UV light increased the level of association of only DmPCNA1. Our observations suggest that DmPCNA2 may function as an independent sliding clamp of DmPCNA1 when DNA repair occurs.
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Affiliation(s)
- Tatsushi Ruike
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Japan
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53
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Shi G, Chang DY, Cheng CC, Guan X, Venclovas Č, Lu AL. Physical and functional interactions between MutY glycosylase homologue (MYH) and checkpoint proteins Rad9-Rad1-Hus1. Biochem J 2006; 400:53-62. [PMID: 16879101 PMCID: PMC1635441 DOI: 10.1042/bj20060774] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 07/24/2006] [Accepted: 08/01/2006] [Indexed: 01/02/2023]
Abstract
The MYH (MutY glycosylase homologue) increases replication fidelity by removing adenines or 2-hydroxyadenine misincorporated opposite GO (7,8-dihydro-8-oxo-guanine). The 9-1-1 complex (Rad9, Rad1 and Hus1 heterotrimer complex) has been suggested as a DNA damage sensor. Here, we report that hMYH (human MYH) interacts with hHus1 (human Hus1) and hRad1 (human Rad1), but not with hRad9. In addition, interactions between MYH and the 9-1-1 complex, from both the fission yeast Schizosaccharomyces pombe and human cells, are partially interchangeable. The major Hus1-binding site is localized to residues 295-350 of hMYH and to residues 245-293 of SpMYH (S. pombe MYH). Val315 of hMYH and Ile261 of SpMYH play important roles for their interactions with Hus1. hHus1 protein and the 9-1-1 complex of S. pombe can enhance the glycosylase activity of SpMYH. Moreover, the interaction of hMYH-hHus1 is enhanced following ionizing radiation. A significant fraction of the hMYH nuclear foci co-localizes with hRad9 foci in H2O2-treated cells. These results reveal that the 9-1-1 complex plays a direct role in base excision repair.
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Key Words
- base excision repair
- dna damage checkpoint
- dna glycosylase
- fission yeast
- hus1
- muty glycosylase homologue (myh)
- the 9-1-1 complex, rad9, rad1 and hus1 heterotrimer complex
- ap, apurinic/apyrimidinic
- ape1, ap endonuclease 1
- atm, ataxia telangiectasia mutated
- atr, atm- and rad3-related protein
- atrip, atr-interacting protein
- brca1, breast-cancer susceptibility gene 1
- dapi, 4′,6′-diamidino-2-phenylindole
- fen1, flap endonuclease 1
- go, 7,8-dihydro-8-oxo-guanine
- gst, glutathione s-transferase
- ha, haemagglutinin
- hhus1, human hus1
- hrad1, human rad1
- msh2, muts homologue 2
- mlh1, mutl homologue 1
- myh, muty glycosylase homologue
- hmyh, human myh
- mmyh, mouse myh
- pcna, proliferating-cell nuclear antigen
- hpcna, human pcna
- rfc, replication factor c
- rmyh, rat myh
- rpa, replication protein a
- sphus1, s. pombe hus1
- spmyh, s. pombe myh
- xpa, xeroderma pigmentosum group a
- xpf, xeroderma pigmentosum group f
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Affiliation(s)
- Guoli Shi
- *Department of Biochemistry and Molecular Biology and Greenebaum Cancer Center, School of Medicine, University of Maryland, Baltimore, MD 21201, U.S.A
| | - Dau-Yin Chang
- *Department of Biochemistry and Molecular Biology and Greenebaum Cancer Center, School of Medicine, University of Maryland, Baltimore, MD 21201, U.S.A
| | - Chih-Chien Cheng
- *Department of Biochemistry and Molecular Biology and Greenebaum Cancer Center, School of Medicine, University of Maryland, Baltimore, MD 21201, U.S.A
| | - Xin Guan
- *Department of Biochemistry and Molecular Biology and Greenebaum Cancer Center, School of Medicine, University of Maryland, Baltimore, MD 21201, U.S.A
| | | | - A-Lien Lu
- *Department of Biochemistry and Molecular Biology and Greenebaum Cancer Center, School of Medicine, University of Maryland, Baltimore, MD 21201, U.S.A
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54
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Doré AS, Kilkenny ML, Jones SA, Oliver AW, Roe SM, Bell SD, Pearl LH. Structure of an archaeal PCNA1-PCNA2-FEN1 complex: elucidating PCNA subunit and client enzyme specificity. Nucleic Acids Res 2006; 34:4515-26. [PMID: 16945955 PMCID: PMC1636371 DOI: 10.1093/nar/gkl623] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The archaeal/eukaryotic proliferating cell nuclear antigen (PCNA) toroidal clamp interacts with a host of DNA modifying enzymes, providing a stable anchorage and enhancing their respective processivities. Given the broad range of enzymes with which PCNA has been shown to interact, relatively little is known about the mode of assembly of functionally meaningful combinations of enzymes on the PCNA clamp. We have determined the X-ray crystal structure of the Sulfolobus solfataricus PCNA1-PCNA2 heterodimer, bound to a single copy of the flap endonuclease FEN1 at 2.9 A resolution. We demonstrate the specificity of interaction of the PCNA subunits to form the PCNA1-PCNA2-PCNA3 heterotrimer, as well as providing a rationale for the specific interaction of the C-terminal PIP-box motif of FEN1 for the PCNA1 subunit. The structure explains the specificity of the individual archaeal PCNA subunits for selected repair enzyme 'clients', and provides insights into the co-ordinated assembly of sequential enzymatic steps in PCNA-scaffolded DNA repair cascades.
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Affiliation(s)
- Andrew S Doré
- CR-UK DNA Repair Enzymes Group, Section of Structural Biology, The Institute of Cancer Research, 237 Fulham Road, Chelsea, London, SW3 6JB, UK.
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55
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Lieberman HB. Rad9, an evolutionarily conserved gene with multiple functions for preserving genomic integrity. J Cell Biochem 2006; 97:690-7. [PMID: 16365875 DOI: 10.1002/jcb.20759] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The Rad9 gene is evolutionarily conserved. Analysis of the gene from yeast, mouse and human reveal roles in multiple, fundamental biological processes primarily but not exclusively important for regulating genomic integrity. The encoded mammalian proteins participate in promoting resistance to DNA damage, cell cycle checkpoint control, DNA repair, and apoptosis. Other functions include a role in embryogenesis, the transactivation of multiple target genes, co-repression of androgen-induced transcription activity of the androgen receptor, a 3'-5' exonuclease activity, and the regulation of ribonucleotide synthesis. Analyses of the functions of Rad9, and in particular its role in regulating and coordinating numerous fundamental biological activities, should not only provide information about the molecular mechanisms of several individual cellular processes, but might also lend insight into the more global control and coordination of what at least superficially present as independent pathways.
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Affiliation(s)
- Howard B Lieberman
- Center for Radiological Research, Columbia University, 630 W. 168th St., New York, New York 10032, USA.
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56
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Brandt PD, Helt CE, Keng PC, Bambara RA. The Rad9 protein enhances survival and promotes DNA repair following exposure to ionizing radiation. Biochem Biophys Res Commun 2006; 347:232-7. [PMID: 16814252 DOI: 10.1016/j.bbrc.2006.06.064] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Accepted: 06/13/2006] [Indexed: 10/24/2022]
Abstract
Following DNA damage cells initiate cell cycle checkpoints to allow time to repair sustained lesions. Rad9, Rad1, and Hus1 proteins form a toroidal complex, termed the 9-1-1 complex, that is involved in checkpoint signaling. 9-1-1 shares high structural similarity to the DNA replication protein proliferating cell nuclear antigen (PCNA) and 9-1-1 has been shown in vitro to stimulate steps of the repair process known as long patch base excision repair. Using a system that allows conditional repression of the Rad9 protein in human cell culture, we show that Rad9, and by extension, the 9-1-1 complex, enhances cell survival, is required for efficient exit from G2-phase arrest, and stimulates the repair of damaged DNA following ionizing radiation. These data provide in vivo evidence that the human 9-1-1 complex participates in DNA repair in addition to its previously described role in DNA damage sensing.
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Affiliation(s)
- Patrick D Brandt
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, The University of Rochester, NY 14642, USA
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57
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Wang W, Lindsey-Boltz LA, Sancar A, Bambara RA. Mechanism of stimulation of human DNA ligase I by the Rad9-rad1-Hus1 checkpoint complex. J Biol Chem 2006; 281:20865-20872. [PMID: 16731526 DOI: 10.1074/jbc.m602289200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Accumulating evidence suggests that the Rad9-Rad1-Hus1 (9-1-1) checkpoint complex, known to be a sensor of DNA damage, is also a component of DNA repair systems. Recent results show that 9-1-1 interacts with several base excision repair proteins. It binds the DNA glycosylase MutY homolog, and stimulates DNA polymerase beta, flap endonuclease 1, and DNA ligase I. 9-1-1 resembles proliferating cell nuclear antigen (PCNA), which stimulates some of these same repair enzymes, and is loaded onto DNA in a similar manner. The complex of 9-1-1 with DNA ligase I can be immunoprecipitated from human cells. Moreover, UV irradiation stimulates 9-1-1.ligase I complex formation, suggesting a role for 9-1-1 in DNA repair. Examining the nature of 9-1-1 interaction with DNA ligase I, we show that there is a similar degree of stimulation on ligation substrates with different structures, and that there is specificity for DNA ligase I. 9-1-1 improves the binding of DNA ligase I to nicked double strand DNA. Furthermore, although high concentrations of casein kinase II strongly inhibits DNA ligase I activity, it does not affect the ability of 9-1-1 to stimulate. This suggests that 9-1-1 is also an activator of DNA ligase I during DNA damage. Unlike PCNA, 9-1-1 stimulates DNA ligase I activity to the same extent on both linear and circular substrates, indicating that encirclement is not a requirement for stimulation. These data are consistent with a direct role for 9-1-1 in DNA repair, but possibly employing a different mechanism than PCNA.
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Affiliation(s)
- Wensheng Wang
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Laura A Lindsey-Boltz
- Department of Biochemistry and Biophysics, CB 7260, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
| | - Aziz Sancar
- Department of Biochemistry and Biophysics, CB 7260, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
| | - Robert A Bambara
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642.
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58
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Rossi ML, Purohit V, Brandt PD, Bambara RA. Lagging strand replication proteins in genome stability and DNA repair. Chem Rev 2006; 106:453-73. [PMID: 16464014 DOI: 10.1021/cr040497l] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Marie L Rossi
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, New York 14642, USA
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59
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Lupardus PJ, Cimprich KA. Phosphorylation of Xenopus Rad1 and Hus1 defines a readout for ATR activation that is independent of Claspin and the Rad9 carboxy terminus. Mol Biol Cell 2006; 17:1559-69. [PMID: 16436514 PMCID: PMC1415302 DOI: 10.1091/mbc.e05-09-0865] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The DNA damage checkpoint pathways sense and respond to DNA damage to ensure genomic stability. The ATR kinase is a central regulator of one such pathway and phosphorylates a number of proteins that have roles in cell cycle progression and DNA repair. Using the Xenopus egg extract system, we have investigated regulation of the Rad1/Hus1/Rad9 complex. We show here that phosphorylation of Rad1 and Hus1 occurs in an ATR- and TopBP1-dependent manner on T5 of Rad1 and S219 and T223 of Hus1. Mutation of these sites has no effect on the phosphorylation of Chk1 by ATR. Interestingly, phosphorylation of Rad1 is independent of Claspin and the Rad9 carboxy terminus, both of which are required for Chk1 phosphorylation. These data suggest that an active ATR signaling complex exists in the absence of the carboxy terminus of Rad9 and that this carboxy-terminal domain may be a specific requirement for Chk1 phosphorylation and not necessary for all ATR-mediated signaling events. Thus, Rad1 phosphorylation provides an alternate and early readout for the study of ATR activation.
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Affiliation(s)
- Patrick J Lupardus
- Department of Molecular Pharmacology, Stanford University, Stanford, CA 94305-5441, USA
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60
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Seo Y, Yan T, Schupp JE, Yamane K, Radivoyevitch T, Kinsella TJ. The Interaction between Two Radiosensitizers: 5-Iododeoxyuridine and Caffeine. Cancer Res 2006; 66:490-8. [PMID: 16397265 DOI: 10.1158/0008-5472.can-05-2766] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
5-Iododeoxyuridine (IUdR) and caffeine are recognized as potential radiosensitizers with different mechanisms of interaction with ionizing radiation (IR). To assess the interaction of these two types of radiosensitizers, we compared treatment responses to these drugs alone and in combination with IR in two p53-proficient and p53-deficient pairs of human colon cancer cell lines (HCT116 versus HCT116 p53-/- and RKO versus RKO E6). Based on clonogenic survival, the three single agents (IR, IUdR, and caffeine) as well as IUdR or caffeine combined with IR are less or equally effective in p53-deficient human tumor cells compared with p53-proficient tumor cells. However, using both radiosensitizers, a significantly greater radiosensitization was found in p53-deficient human tumor cells. To better understand the interaction of these two radiosensitizers, additional studies on DNA repair and cell cycle regulation were done. We found that caffeine enhanced IUdR-DNA incorporation and IUdR-mediated radiosensitization by partially inhibiting repair (removal) of IUdR in DNA. The repair of IR-induced DNA double-strand breaks was also inhibited by caffeine. However, these effects of caffeine on IUdR-mediated radiosensitization were not found in p53-proficient cells. Cell cycle analyses also showed a greater abrogation of IR-induced S- and G2-phase arrests by caffeine in p53-deficient cells, particularly when combined with IUdR. Collectively, these data provide the mechanistic bases for combining these two radiosensitizers to enhance tumor cytotoxicity. This differential dual mode of radiosensitization by combining IUdR and caffeine-like drugs (e.g., UCN-01) in p53-deficient human tumors may lead to a greater therapeutic gain.
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Affiliation(s)
- Yuji Seo
- Department of Radiation Oncology, Case Western Reserve University School of Medicine and University Hospitals of Cleveland/Ireland Cancer Center, Cleveland, Ohio 44106-6068, USA
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61
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Smirnova E, Toueille M, Markkanen E, Hübscher U. The human checkpoint sensor and alternative DNA clamp Rad9-Rad1-Hus1 modulates the activity of DNA ligase I, a component of the long-patch base excision repair machinery. Biochem J 2005; 389:13-7. [PMID: 15871698 PMCID: PMC1184534 DOI: 10.1042/bj20050211] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The human checkpoint sensor and alternative clamp Rad9-Rad1-Hus1 can interact with and specifically stimulate DNA ligase I. The very recently described interactions of Rad9-Rad1-Hus1 with MutY DNA glycosylase, DNA polymerase beta and Flap endonuclease 1 now complete our view that the long-patch base excision machinery is an important target of the Rad9-Rad1-Hus1 complex, thus enhancing the quality control of DNA.
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Affiliation(s)
- Ekaterina Smirnova
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich-Irchel, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - Magali Toueille
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich-Irchel, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - Enni Markkanen
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich-Irchel, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - Ulrich Hübscher
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich-Irchel, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
- To whom correspondence should be addressed (email )
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62
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Friedrich-Heineken E, Toueille M, Tännler B, Bürki C, Ferrari E, Hottiger MO, Hübscher U. The two DNA clamps Rad9/Rad1/Hus1 complex and proliferating cell nuclear antigen differentially regulate flap endonuclease 1 activity. J Mol Biol 2005; 353:980-9. [PMID: 16216273 DOI: 10.1016/j.jmb.2005.09.018] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 08/05/2005] [Accepted: 09/07/2005] [Indexed: 11/22/2022]
Abstract
DNA damage leads to activation of several mechanisms such as DNA repair and cell-cycle checkpoints. It is evident that these different cellular mechanisms have to be finely co-ordinated. Growing evidence suggests that the Rad9/Rad1/Hus1 cell-cycle checkpoint complex (9-1-1 complex), which is recruited to DNA lesion upon DNA damage, plays a major role in DNA repair. This complex has been shown to interact with and stimulate several proteins involved in long-patch base excision repair. On the other hand, the well-characterised DNA clamp-proliferating cell nuclear antigen (PCNA) also interacts with and stimulates several of these factors. In this work, we compared the effects of the 9-1-1 complex and PCNA on flap endonuclease 1 (Fen1). Our data suggest that PCNA and the 9-1-1 complex can independently bind to and activate Fen1. Finally, acetylation of Fen1 by p300-HAT abolished the stimulatory effect of the 9-1-1 complex but not that of PCNA, suggesting a possible mechanism of regulation of this important repair pathway.
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Affiliation(s)
- Erica Friedrich-Heineken
- Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich-Irchel, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
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63
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Sabbioneda S, Minesinger BK, Giannattasio M, Plevani P, Muzi-Falconi M, Jinks-Robertson S. The 9-1-1 checkpoint clamp physically interacts with polzeta and is partially required for spontaneous polzeta-dependent mutagenesis in Saccharomyces cerevisiae. J Biol Chem 2005; 280:38657-65. [PMID: 16169844 DOI: 10.1074/jbc.m507638200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The use of translesion synthesis (TLS) polymerases to bypass DNA lesions during replication constitutes an important mechanism to restart blocked/stalled DNA replication forks. Because TLS polymerases generally have low fidelity on undamaged DNA, the cell must regulate the interaction of TLS polymerases with damaged versus undamaged DNA to maintain genome integrity. The Saccharomyces cerevisiae checkpoint proteins Ddc1, Rad17, and Mec3 form a clamp-like structure (the 9-1-1 clamp) that has physical similarity to the homotrimeric sliding clamp proliferating cell nuclear antigen, which interacts with and promotes the processivity of the replicative DNA polymerases. In this work, we demonstrate both an in vivo and in vitro physical interaction between the Mec3 and Ddc1 subunits of the 9-1-1 clamp and the Rev7 subunit of the Polzeta TLS polymerase. In addition, we demonstrate that loss of Mec3, Ddc1, or Rad17 results in a decrease in Polzeta-dependent spontaneous mutagenesis. These results suggest that, in addition to its checkpoint signaling role, the 9-1-1 clamp may physically regulate Polzeta-dependent mutagenesis by controlling the access of Polzeta to damaged DNA.
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Affiliation(s)
- Simone Sabbioneda
- Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Milano, Italy 20133
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64
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Current awareness on yeast. Yeast 2005; 22:745-52. [PMID: 16106592 DOI: 10.1002/yea.1165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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