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Castán A, Fernández-Calleja V, Hernández P, Krimer DB, Schvartzman JB, Fernández-Nestosa MJ. Analysis of DNA topology of EBV minichromosomes in HEK 293 cells. PLoS One 2017; 12:e0188172. [PMID: 29186176 PMCID: PMC5706722 DOI: 10.1371/journal.pone.0188172] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 10/30/2017] [Indexed: 11/21/2022] Open
Abstract
Simian Virus 40 (SV40) and Epstein-Barr Virus (EBV) are frequently used as model systems to study DNA replication. Their genomes are both circular duplex DNAs organized in a single replicon where replication initiates at a precise site upon binding of a specific protein: the large tumor (T) antigen for SV40 and the Epstein-Barr Nuclear Antigen 1 (EBNA-1) for EBV. Despite the abundant information available on the genetics and biochemistry of the replication process in these systems, little is known about the changes in DNA topology that take place as molecules are transfected into eukaryotic cells, assembled into chromatin and bind initiator proteins to start replication. Here we used high-resolution two-dimensional agarose gel electrophoresis to demonstrate that in Human Embryonic Kidney (HEK) 293 cells, minichromosomes of almost the same mass carrying either the SV40 or the EBV replication origin showed similar topological features. The patterns were very similar regardless of the initiator proteins. We also showed that in a hybrid minichromosome, pEco3’Δ, that initiates replication from the SV40 origin, the presence of EBNA-1 and its putative binding to the EBV “family of repeats” induces no significant topological change. These observations challenge the idea that binding of EBNA-1 to oriP could induce negative supercoiling and favor a model suggesting that it binds to oriP in a two-step process where only the second step causes structural changes in a transient cell cycle specific manner.
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Affiliation(s)
- Alicia Castán
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, Madrid, Spain
| | - Vanessa Fernández-Calleja
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, Madrid, Spain
| | - Pablo Hernández
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, Madrid, Spain
| | - Dora B. Krimer
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, Madrid, Spain
| | - Jorge B. Schvartzman
- Department of Cellular and Molecular Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, Madrid, Spain
- * E-mail: (JBS); (JFN)
| | - María-José Fernández-Nestosa
- Scientific and Applied Computing Laboratory, Polytechnic School, National University of Asunción, SL, San Lorenzo, Paraguay
- * E-mail: (JBS); (JFN)
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Tuteja N, Tran NQ, Dang HQ, Tuteja R. Plant MCM proteins: role in DNA replication and beyond. PLANT MOLECULAR BIOLOGY 2011; 77:537-45. [PMID: 22038093 DOI: 10.1007/s11103-011-9836-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 10/09/2011] [Indexed: 05/18/2023]
Abstract
Mini-chromosome maintenance (MCM) proteins form heterohexameric complex (MCM2-7) to serve as licensing factor for DNA replication to make sure that genomic DNA is replicated completely and accurately once during S phase in a single cell cycle. MCMs were initially identified in yeast for their role in plasmid replication or cell cycle progression. Each of six MCM contains highly conserved sequence called "MCM box", which contains two ATPase consensus Walker A and Walker B motifs. Studies on MCM proteins showed that (a) the replication origins are licensed by stable binding of MCM2-7 to form pre-RC (pre-replicative complex) during G1 phase of the cell cycle, (b) the activation of MCM proteins by CDKs (cyclin-dependent kinases) and DDKs (Dbf4-dependent kinases) and their helicase activity are important for pre-RC to initiate the DNA replication, and (c) the release of MCMs from chromatin renders the origins "unlicensed". DNA replication licensing in plant is, in general, less characterized. The MCMs have been reported from Arabidopsis, maize, tobacco, pea and rice, where they are found to be highly expressed in dividing tissues such as shoot apex and root tips, localized in nucleus and cytosol and play important role in DNA replication, megagametophyte and embryo development. The identification of six MCM coding genes from pea and Arabidopsis suggest six distinct classes of MCM protein in higher plant, and the conserved function right across the eukaryotes. This overview of MCMs contains an emphasis on MCMs from plants and the novel role of MCM6 in abiotic stress tolerance.
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Affiliation(s)
- Narendra Tuteja
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
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3
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Abstract
Eukaryotic DNA replication is regulated to ensure all chromosomes replicate once and only once per cell cycle. Replication begins at many origins scattered along each chromosome. Except for budding yeast, origins are not defined DNA sequences and probably are inherited by epigenetic mechanisms. Initiation at origins occurs throughout the S phase according to a temporal program that is important in regulating gene expression during development. Most replication proteins are conserved in evolution in eukaryotes and archaea, but not in bacteria. However, the mechanism of initiation is conserved and consists of origin recognition, assembly of prereplication (pre-RC) initiative complexes, helicase activation, and replisome loading. Cell cycle regulation by protein phosphorylation ensures that pre-RC assembly can only occur in G1 phase, whereas helicase activation and loading can only occur in S phase. Checkpoint regulation maintains high fidelity by stabilizing replication forks and preventing cell cycle progression during replication stress or damage.
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Affiliation(s)
- R A Sclafani
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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4
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Wegrzyn G, Wegrzyn A. Genetic switches during bacteriophage lambda development. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2005; 79:1-48. [PMID: 16096026 DOI: 10.1016/s0079-6603(04)79001-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- Grzegorz Wegrzyn
- Department of Molecular Biology, University of Gdańsk, 80-822 Gdańsk, Poland
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Sclafani RA, Fletcher RJ, Chen XS. Two heads are better than one: regulation of DNA replication by hexameric helicases. Genes Dev 2004; 18:2039-45. [PMID: 15342486 PMCID: PMC2292464 DOI: 10.1101/gad.1240604] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Robert. A. Sclafani
- Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
| | - Ryan J. Fletcher
- Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
- Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089, USA
| | - Xiaojiang S. Chen
- Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
- Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089, USA
- Corresponding author: E-MAIL or ; FAX (303) 315-8113
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6
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Das S, Mukherjee C, Sinha P, Lohia A. Constitutive association of Mcm2-3-5 proteins with chromatin in Entamoeba histolytica. Cell Microbiol 2004; 7:259-67. [PMID: 15659069 DOI: 10.1111/j.1462-5822.2004.00456.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Eukaryotic cells duplicate their genome once and only once per cell cycle. Our earlier studies with the protozoan parasite, Entamoeba histolytica, have shown that genome reduplication may occur several times without nuclear or cellular division. The Mcm2-7 protein complex is required for licensing of DNA replication. In an effort to understand whether genome reduplication occurs due to absence or failure of the DNA replication licensing system, we analysed the function of Mcm2-3-5 proteins in E. histolytica. In this study, we have cloned E. histolytica (Eh) MCM2 and Eh MCM5 genes, while Eh MCM3 was cloned earlier. The sequence of Eh MCM2-3-5 genes is well conserved with other eukaryotic homologues. We have shown that Eh Mcm2,3 proteins are functional in Saccharomyces cerevisiae. Our studies in E. histolytica showed that Eh Mcm2-3-5 proteins are associated with chromatin constitutively in cycling cells and during arrest of DNA synthesis induced by serum starvation. Alternation of genome duplication with mitosis is regulated by association-dissociation of Mcm2-7 proteins with chromatin in other eukaryotes. Our results suggest that constitutive association of Mcm proteins with chromatin could be one of the reasons why genome reduplication occurs in E. histolytica.
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Affiliation(s)
- Suchismita Das
- Department of Biochemistry, Bose Institute, P1/12 CIT Scheme VIIM, Kolkata 700054, India
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7
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Bradshaw EM, Sanford DG, Luo X, Sudmeier JL, Gurard-Levin ZA, Bullock PA, Bachovchin WW. T antigen origin-binding domain of simian virus 40: determinants of specific DNA binding. Biochemistry 2004; 43:6928-36. [PMID: 15170330 DOI: 10.1021/bi030228+] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To better understand origin recognition and initiation of DNA replication, we have examined by NMR complexes formed between the origin-binding domain of SV40 T antigen (T-ag-obd), the initiator protein of the SV40 virus, and cognate and noncognate DNA oligomers. The results reveal two structural effects associated with "origin-specific" binding that are absent in nonspecific DNA binding. The first is the formation of a hydrogen bond (H-bond) involving His 203, a residue that genetic studies have previously identified as crucial to both specific and nonspecific DNA binding in full-length T antigen. In free T-ag-obd, the side chain of His 203 has a pK(a) value of approximately 5, titrating to the N(epsilon)(1)H tautomer at neutral pH (Sudmeier, J. L., et al. (1996) J. Magn. Reson., Ser. B 113, 236-247). In complexes with origin DNA, His 203 N(delta)(1) becomes protonated and remains nontitrating as the imidazolium cation at all pH values from 4 to 8. The H-bonded N(delta1)H resonates at 15.9 ppm, an unusually large N-H proton chemical shift, of a magnitude previously observed only in the catalytic triad of serine proteases at low pH. The formation of this H-bond requires the middle G/C base pair of the recognition pentanucleotide, GAGGC. The second structural effect is a selective distortion of the A/T base pair characterized by a large (0.6 ppm) upfield chemical-shift change of its Watson-Crick proton, while nearby H-bonded protons remain relatively unaffected. The results indicate that T antigen, like many other DNA-binding proteins, may employ "catalytic" or "transition-state-like" interactions in binding its cognate DNA (Jen-Jacobson, L. (1997) Biopolymers 44, 153-180), which may be the solution to the well-known paradox between the relatively modest DNA-binding specificity exhibited by initiator proteins and the high specificity of initiation.
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Affiliation(s)
- Elizabeth M Bradshaw
- Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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8
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Lee JK, Seo YS, Hurwitz J. The Cdc23 (Mcm10) protein is required for the phosphorylation of minichromosome maintenance complex by the Dfp1-Hsk1 kinase. Proc Natl Acad Sci U S A 2003; 100:2334-9. [PMID: 12604790 PMCID: PMC151341 DOI: 10.1073/pnas.0237384100] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Previous studies in Saccharomyces cerevisiae have defined an essential role for the Dbf4-Cdc7 kinase complex in the initiation of DNA replication presumably by phosphorylation of target proteins, such as the minichromosome maintenance (Mcm) complex. We have examined the phosphorylation of the Mcm complex by the Dfp1-Hsk1 kinase, the Schizosaccharomyces pombe homologue of Dbf4-Cdc7. In vitro, the purified Dfp1-Hsk1 kinase efficiently phosphorylated Mcm2p. In contrast, Mcm2p, present in the six-subunit Mcm complex, was a poor substrate of this kinase and required Cdc23p (homologue of Mcm10p) for efficient phosphorylation. In the presence of Cdc23p, Dfp1-Hsk1 phosphorylated the Mcm2p and Mcm4p subunits of the Mcm complex. Cdc23p interacted with both the Mcm complex and Dfp1-Hsk1 by selectively binding to the Mcm467 subunits and Dfp1p, respectively. The N terminus of Cdc23p was found to interact directly with Dfp1-Hsk1 and was essential for phosphorylation of the Mcm complex. Truncated derivatives of Cdc23p that complemented the temperature-sensitive phenotype of cdc23 mutant cells also stimulated the phosphorylation of Mcm complex, implying that this activity might be a critical role of Cdc23p in vivo. These results suggest that Cdc23p participates in the activation of prereplicative complex by recruiting the Dfp1-Hsk1 kinase and stimulating the phosphorylation of the Mcm complex.
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Affiliation(s)
- Joon-Kyu Lee
- Program in Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
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9
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Stubbs MC, Hall DJ. The amino-terminus of the E2F-1 transcription factor inhibits DNA replication of autonomously replicating plasmids in mammalian cells. Oncogene 2002; 21:3715-26. [PMID: 12032840 DOI: 10.1038/sj.onc.1205473] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2001] [Revised: 03/07/2002] [Accepted: 03/11/2002] [Indexed: 11/10/2022]
Abstract
The E2F1 transcription factor plays a pivotal role in driving cells out of a quiescent state and into the S phase of the cell cycle, in part by transactivating genes needed for DNA replication including DHFR, thymidine kinase, and DNA Polymerase alpha. E2F1 has also been implicated in regulating an S phase checkpoint, however its role in this checkpoint is not well defined. To determine how E2F1 affects such a checkpoint, we utilized an in vivo replication assay employing a plasmid based SV40 origin of replication, transfected into cells expressing SV40 large T antigen. Here we show that expression of full length E2F1, or only its N terminus, represses replication from plasmids containing the SV40 origin, while N terminal deletions of E2F1 do not. E2F1 appears to inhibit the elongation phase of replication and not the initiation phase since it does not affect the replication of other cotransfected plasmids containing only the SV40 origin. Further, inhibition of replication is dependent on both the amino-terminus of the E2F1 protein and on a DNA sequence that is contained within the 3' end of the E2F1 cDNA. Additionally, both full-length E2F1, or just its N-terminus, form protein complexes with two portions of the 3' end of the E2F1 cDNA. These data provide a clue to the mechanism by which E2F1 regulates transit through the S phase checkpoint, by acting on a specific DNA sequence via its amino-terminal region, to inhibit elongation of DNA replication.
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Affiliation(s)
- Matthew C Stubbs
- Cartilage and Orthopaedic Branch, National Institutes of Arthritis and Musculoskeletal and Skin Diseases, NIH, MSC 5755, 9000 Rockville Pike, Bethesda, Maryland, MD 20892, USA
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10
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Kautz AR, Weisshart K, Schneider A, Grosse F, Nasheuer HP. Amino acids 257 to 288 of mouse p48 control the cooperation of polyomavirus large T antigen, replication protein A, and DNA polymerase alpha-primase to synthesize DNA in vitro. J Virol 2001; 75:8569-78. [PMID: 11507202 PMCID: PMC115102 DOI: 10.1128/jvi.75.18.8569-8578.2001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although p48 is the most conserved subunit of mammalian DNA polymerase alpha-primase (pol-prim), the polypeptide is the major species-specific factor for mouse polyomavirus (PyV) DNA replication. Human and murine p48 contain two regions (A and B) that show significantly lower homology than the rest of the protein. Chimerical human-murine p48 was prepared and coexpressed with three wild-type subunits of pol-prim, and four subunit protein complexes were purified. All enzyme complexes synthesized DNA on single-stranded (ss) DNA and replicated simian virus 40 DNA. Although the recombinant protein complexes physically interacted with PyV T antigen (Tag), we determined that the murine region A mediates the species specificity of PyV DNA replication in vitro. More precisely, the nonconserved phenylalanine 262 of mouse p48 is crucial for this activity, and pol-prim with mutant p48, h-S262F, supports PyV DNA replication in vitro. DNA synthesis on RPA-bound ssDNA revealed that amino acid (aa) 262, aa 266, and aa 273 to 288 are involved in the functional cooperation of RPA, pol-prim, and PyV Tag.
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Affiliation(s)
- A R Kautz
- Abteilung Biochemie, Institut für Molekulare Biotechnologie e.V., D-07745 Jena, Germany
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11
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Burke TW, Cook JG, Asano M, Nevins JR. Replication factors MCM2 and ORC1 interact with the histone acetyltransferase HBO1. J Biol Chem 2001; 276:15397-408. [PMID: 11278932 DOI: 10.1074/jbc.m011556200] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The minichromosome maintenance (MCM) proteins, together with the origin recognition complex (ORC) proteins and Cdc6, play an essential role in eukaryotic DNA replication through the formation of a pre-replication complex at origins of replication. We used a yeast two-hybrid screen to identify MCM2-interacting proteins. One of the proteins we identified is identical to the ORC1-interacting protein termed HBO1. HBO1 belongs to the MYST family, characterized by a highly conserved C2HC zinc finger and a putative histone acetyltransferase domain. Biochemical studies confirmed the interaction between MCM2 and HBO1 in vitro and in vivo. An N-terminal domain of MCM2 is necessary for binding to HBO1, and a C2HC zinc finger of HBO1 is essential for binding to MCM2. A reverse yeast two-hybrid selection was performed to isolate an allele of MCM2 that is defective for interaction with HBO1; this allele was then used to isolate a suppressor mutant of HBO1 that restores the interaction with the mutant MCM2. This suppressor mutation was located in the HBO1 zinc finger. Taken together, these findings strongly suggest that the interaction between MCM2 and HBO1 is direct and mediated by the C2HC zinc finger of HBO1. The biochemical and genetic interactions of MYST family protein HBO1 with two components of the replication apparatus, MCM2 and ORC1, suggest that HBO1-associated HAT activity may play a direct role in the process of DNA replication.
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Affiliation(s)
- T W Burke
- Department of Genetics, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA
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12
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Barańska S, Gabig M, Węgrzyn A, Konopa G, Herman-Antosiewicz A, Hernandez P, Schvartzman JB, Helinski DR, Węgrzyn G. Regulation of the switch from early to late bacteriophage lambda DNA replication. MICROBIOLOGY (READING, ENGLAND) 2001; 147:535-547. [PMID: 11238961 DOI: 10.1099/00221287-147-3-535] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
There are two modes of bacteriophage lambda DNA replication following infection of its host, Escherichia coli. Early after infection, replication occurs according to the theta (theta or circle-to-circle) mode, and is later switched to the sigma (sigma or rolling-circle) mode. It is not known how this switch, occurring at a specific time in the infection cycle, is regulated. Here it is demonstrated that in wild-type cells the replication starting from orilambda proceeds both bidirectionally and unidirectionally, whereas in bacteria devoid of a functional DnaA protein, replication from orilambda is predominantly unidirectional. The regulation of directionality of replication from orilambda is mediated by positive control of lambda p(R) promoter activity by DnaA, since the mode of replication of an artificial lambda replicon bearing the p(tet) promoter instead of p(R) was found to be independent of DnaA function. These findings and results of density-shift experiments suggest that in dnaA mutants infected with lambda, phage DNA replication proceeds predominantly according to the unidirectional theta mechanism and is switched early after infection to the sigma mode. It is proposed that in wild-type E. coli cells infected with lambda, phage DNA replication proceeds according to a bidirectional theta mechanism early after infection due to efficient transcriptional activation of orilambda, stimulated by the host DnaA protein. After a few rounds of this type of replication, the resulting increased copy number of lambda genomic DNA may cause a depletion of free DnaA protein because of its interaction with the multiple DnaA-binding sites in lambda DNA. It is proposed that this may lead to inefficient transcriptional activation of orilambda resulting in unidirectional theta replication followed by sigma type replication.
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Affiliation(s)
- Sylwia Barańska
- Department of Molecular Biology, University of Gdańsk1 and Laboratory of Molecular Biology (affiliated with the University of Gdańsk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences2, Kładki 24, 80-822 Gdańsk, Poland
| | - Magdalena Gabig
- Department of Molecular Biology, University of Gdańsk1 and Laboratory of Molecular Biology (affiliated with the University of Gdańsk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences2, Kładki 24, 80-822 Gdańsk, Poland
| | - Alicja Węgrzyn
- Department of Molecular Biology, University of Gdańsk1 and Laboratory of Molecular Biology (affiliated with the University of Gdańsk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences2, Kładki 24, 80-822 Gdańsk, Poland
| | - Grażyna Konopa
- Department of Molecular Biology, University of Gdańsk1 and Laboratory of Molecular Biology (affiliated with the University of Gdańsk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences2, Kładki 24, 80-822 Gdańsk, Poland
| | - Anna Herman-Antosiewicz
- Department of Molecular Biology, University of Gdańsk1 and Laboratory of Molecular Biology (affiliated with the University of Gdańsk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences2, Kładki 24, 80-822 Gdańsk, Poland
| | - Pablo Hernandez
- Departamento de Biologı́a Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Velázquez 144, 28006 Madrid, Spain3
| | - Jorge B Schvartzman
- Departamento de Biologı́a Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Velázquez 144, 28006 Madrid, Spain3
| | - Donald R Helinski
- Center for Molecular Genetics and Department of Biology, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA4
| | - Grzegorz Węgrzyn
- Marine Biology Center, Polish Academy of Sciences, Św. Wojciecha 5, 81-347 Gdynia, Poland5
- Department of Molecular Biology, University of Gdańsk1 and Laboratory of Molecular Biology (affiliated with the University of Gdańsk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences2, Kładki 24, 80-822 Gdańsk, Poland
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13
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Organization, Replication, Transposition, and Repair of DNA. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50030-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Vande Berg JS, Smith PD, Haywood-Reid PL, Munson AB, Soules KA, Robson MC. Dynamic forces in the cell cycle affecting fibroblasts in pressure ulcers. Wound Repair Regen 2001; 9:19-27. [PMID: 11350636 DOI: 10.1046/j.1524-475x.2001.00019.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Utilizing specific cell cycle markers of gene activity, temporal changes in the equilibrium of proliferating and non proliferating fibroblasts were shown in pressure ulcers after 36 days of quality care. Average cell counts from multiple tissue sections showed that fibroblast nuclei were stained in decreasing order by antibodies to p21, p21/proliferating cell nuclear antigen (PCNA) and PCNA. P21 labeling suggested that the majority of ulcer fibroblasts were senescent. Fibroblast nuclei showing PCNA staining identified those fibroblasts that were capable of synthesizing DNA and contributing to pressure ulcer repair. Increased rates of wound closure were correlated with a decreasing number of p21 positive cells and an increasing portion of PCNA labeled cells. While the proportion of antigens appeared to correlate with the status of wound closure after 36 days of quality care, they did not always appear to reflect the final outcome of the pressure ulcer. No significant differences were observed in ulcer fibroblasts labeled with p21 at 0 and 10 days, however, the differences were significant after 36 days of quality care (p = 0.05, analysis of variance, post hoc Tukey test). The cellular contribution to pressure ulcer repair appeared to occur from ulcer fibroblasts that were capable of division, of emerging from quiescence, and that were successful in repairing their DNA.
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Affiliation(s)
- J S Vande Berg
- San Diego Veterans Administration Medical Center, University of California, San Diego, California, USA
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15
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Potrykus K, Wróbel B, Wegrzyn A, Wegrzyn G. Replication of oriJ-based plasmid DNA during the stringent and relaxed responses of Escherichia coli. Plasmid 2000; 44:111-26. [PMID: 10964622 DOI: 10.1006/plas.2000.1462] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The oriJ-based plasmids contain the origin of DNA replication from the cryptic Rac prophage, present in the chromosomes of most Escherichia coli K-12 strains. The organization of the oriJ replication region resembles that of the bacteriophage lambda, although sequence similarity is small. Here we investigated the regulation of replication of the oriJ-based plasmid in E. coli relA(+) and relA(-) hosts during amino acid starvation and limitation, i.e., during the stringent and relaxed responses. We found that, contrary to plasmids derived from phage lambda, replication of the oriJ-based plasmid proceeds efficiently during both stringent and relaxed responses. On the other hand, density shift experiments and measurement of the stability of a putative replication initiator protein (the lambda O protein homologue) suggest that this replication may be carried out by the heritable replication complex, as previously demonstrated for lambda plasmids. We demonstrate that contrary to bacteriophage lambda p(R) promoter, an analogous promoter from the oriJ region is activated rather than inhibited at increased ppGpp levels. We propose that various responses of these promoters (p(R) and p(R-Rac), which are necessary for transcriptional activation of orilambda and perhaps oriJ, respectively) to ppGpp are responsible for differences in the replication regulation between orilambda- and oriJ-based plasmids during the stringent response.
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Affiliation(s)
- K Potrykus
- Department of Molecular Biology, University of Gdańsk, Kladki 24, Gdańsk, 80-822, Poland
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16
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Abstract
The MCM proteins are essential replication initiation factors originally identified as proteins required for minichromosome maintenance in Saccharomyces cerevisiae. The best known among them are a family of six structurally related proteins, MCM2-7, which are evolutionally conserved in all eukaryotes. The MCM2-7 proteins form a hexameric complex. This complex is a key component of the prereplication complex that assembles at replication origins during early G1 phase. New evidence suggests that the MCM2-7 proteins may be involved not only in the initiation but also in the elongation of DNA replication. Orchestration of the functional interactions between the MCM2-7 proteins and other components of the prereplication complex by cell cycle-dependent protein kinases results in initiation of DNA synthesis once every cell cycle.
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Affiliation(s)
- B K Tye
- Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853-2703, USA
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17
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Lee JK, Hurwitz J. Isolation and characterization of various complexes of the minichromosome maintenance proteins of Schizosaccharomyces pombe. J Biol Chem 2000; 275:18871-8. [PMID: 10770926 DOI: 10.1074/jbc.m001118200] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Minichromosome maintenance (Mcm) proteins 2-7 are highly conserved in eukaryotes and play an essential role in DNA replication. Here, we describe the reconstitution of the various complexes of the Mcm proteins of Schizosaccharomyces pombe using the baculovirus expression system. The simultaneous expression of all six of the Mcm proteins, as well as different combinations of these proteins, yielded several stable complexes that included the heterohexamer of Mcm2/3/4/5/6/7, the Mcm2/4/6/7 heterotetramer, the dimer of the Mcm4/6/7 heterotrimer, and the Mcm3/5 heterodimer. The purification and characterization of the biochemical properties of these complexes showed that only the dimeric complex of the Mcm4/6/7 heterotrimer possessed single stranded DNA-dependent ATPase, ATP-dependent single stranded DNA binding, and 3' to 5' DNA helicase activities. Consistent with these results, the interaction of either Mcm2 or Mcm3/5 with the Mcm4/6/7 complex resulted in the disassembly of the dimeric complex of Mcm4/6/7 and the loss of DNA helicase activity. These results suggest that the Mcm4/6/7 complex is a catalytic core of the Mcm complex and that Mcm2 and Mcm3/5 may be involved in the regulation of the activity of this complex.
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Affiliation(s)
- J K Lee
- Graduate Program in Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA
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18
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Abstract
Great insight into the molecular details of cell cycle regulation has been obtained in the past decade. However, most of the progress has been in defining the regulation of the family of cyclin-dependent kinases (CDKs). Recent studies of a myriad of eukaryotic organisms have defined both the regulation and substrates of Cdc7p kinase, which forms a CDK-cyclin-like complex with Dbf4p, is necessary for the initiation of DNA replication and has been conserved in evolution. This kinase is also required for the induction of mutations after DNA damage and for commitment to recombination in the meiotic cell cycle. However, less is known about the role of the kinase in these processes. In a manner similar to CDKs, Cdc7p is activated by a regulatory subunit, Dbf4, the levels of which fluctuate during the cell cycle. One or more subunits of the conserved MCM helicase complex at chromosomal origins of DNA replication are substrates for the kinase during S phase. Phosphorylation of the MCM complex by Cdc7p-Dbf4p might activate DNA replication by unwinding DNA. Therefore, activation of Cdc7p is required for DNA replication. Given that Cdc7p-Dbf4 kinase is overexpressed in many neoplastic cells and tumors, it might be an important early biomarker during cancer progression.
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Affiliation(s)
- R A Sclafani
- Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
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19
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Konopa G, Barańska S, Wegrzyn A, Wegrzyn G. Bacteriophage and host mutants causing the rolling-circle lambda DNA replication early after infection. FEBS Lett 2000; 472:217-20. [PMID: 10788614 DOI: 10.1016/s0014-5793(00)01451-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
There are two modes of bacteriophage lambda DNA replication during its lytic development in Escherichia coli cells. The circle-to-circle (theta) replication predominates at early stages of the phage growth, whereas rolling-circle (sigma) replication occurs late after infection to produce long concatemers that serve as substrates for packaging of lambda DNA into phage proheads. The mechanism regulating the switch from theta to sigma replication remains unknown. Our previous genetic studies indicated that the bacteriophage lambda Pts1piA66 mutant cannot replicate at 43 degrees C in the wild-type E. coli host, but it can replicate in the dnaA46(ts) mutant. Density shift experiments suggested that the parental DNA molecules of the infecting phage enter sigma replication. Here, using electron microscopy, we demonstrate that as soon as 5 min after infection of the dnaA46(ts) mutant by the lambdaPts1piA66 phage at 43 degrees C, the sigma replication intermediates are highly predominant over theta replication intermediates, contrary to the wild-type conditions (wild-type bacteria infected with the lambdaP(+) phage). The initiation of replication of the lambdaPts1piA66 mutant at 43 degrees C was strongly inhibited in the dnaA(+) host, as demonstrated by electron microscopy and by pulse-labeling of the phage-derived plasmid replicon. Implications for the mechanism of the regulation of the switch from theta to sigma replication mode are discussed.
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Affiliation(s)
- G Konopa
- Department of Molecular Biology, University of Gdańsk, Kladki 24, 80-822, Gdańsk, Poland
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20
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Masumoto H, Sugino A, Araki H. Dpb11 controls the association between DNA polymerases alpha and epsilon and the autonomously replicating sequence region of budding yeast. Mol Cell Biol 2000; 20:2809-17. [PMID: 10733584 PMCID: PMC85497 DOI: 10.1128/mcb.20.8.2809-2817.2000] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dpb11 is required for chromosomal DNA replication and the S-phase checkpoint in Saccharomyces cerevisiae. Here, we report detection of a physical complex containing Dpb11 and DNA polymerase epsilon (Dpb11-Polepsilon complex). During the S phase of the cell cycle, Dpb11 associated preferentially with DNA fragments containing autonomously replicating sequences (ARSs), at the same time as Polepsilon associated with these fragments. Association of Dpb11 and Polepsilon with these fragments was mutually dependent, suggesting that the Dpb11-Polepsilon complex associates with the ARS. Moreover, Dpb11 was required for the association of Polalpha-primase with the fragments. Thus, it seems likely that association of the Dpb11-Polepsilon complex with the ARS fragments is required for the association of the Polalpha-primase complex. Hydroxyurea inhibits late-origin firing in S. cerevisiae, and the checkpoint genes, RAD53 and MEC1, are involved in this inhibition. In the presence of hydroxyurea at temperatures permissive for cell growth, Polepsilon in dpb11-1 cells associated with early- and late-origin fragments. In wild-type cells, however, it associated only with early-origin fragments. This indicates that Dpb11 may also be involved in the regulation of late-origin firing. Overall, these results suggest that Dpb11 controls the association between DNA polymerases alpha and epsilon and the ARS.
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Affiliation(s)
- H Masumoto
- Division of Microbial Genetics, National Institute of Genetics, Shizuoka, Japan
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21
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Abstract
Minichromosome maintenance (mcm) is an effective genetic assay for mutants defective in DNA replication. Two classes of mcm mutants have been identified using this screen: those that differentially affect the activities of certain autonomously replicating sequences (ARSs) and those that uniformly affect the activities of all ARSs. The ARS-specific MCM genes are essential for the initiation of DNA replication. Among these are members of the MCM2-7 family that encode subunits of the preinitiation complex and MCM10, whose gene product interacts with members of the Mcm2-7 proteins. Among the ARS-nonspecific MCM gene products are chromosome transmission factors. Refinement of this genetic assay as a screening tool and further analysis of existing mcm mutants may reveal new replication initiation proteins.
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Affiliation(s)
- B K Tye
- Section of Biochemistry Molecular and Cell Biology, Cornell University, Ithaca, New York 14853-2703, USA
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22
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Araujo FD, Knox JD, Ramchandani S, Pelletier R, Bigey P, Price G, Szyf M, Zannis-Hadjopoulos M. Identification of initiation sites for DNA replication in the human dnmt1 (DNA-methyltransferase) locus. J Biol Chem 1999; 274:9335-41. [PMID: 10092611 DOI: 10.1074/jbc.274.14.9335] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vertebrates have developed multiple mechanisms to coordinate the replication of epigenetic and genetic information. Dnmt1 encodes the maintenance enzyme DNA-methyltransferase, which is responsible for propagating the DNA methylation pattern and the epigenetic information that it encodes during replication. Direct sequence analysis and bisulfite mapping of the 5' region of DNA-methyltransferase 1 (dnmt1) have indicated the presence of many sequence elements associated with previously characterized origins of DNA replication. This study tests the hypothesis that the dnmt1 region containing these elements is an origin of replication in human cells. First, we demonstrate that a vector containing this dnmt1 sequence is able to support autonomous replication when transfected into HeLa cells. Second, using a gel retardation assay, we show that it contains a site for binding of origin-rich sequences binding activity, a recently purified replication protein. Finally, using competitive polymerase chain reaction, we show that replication initiates in this region in vivo. Based on these lines of evidence, we propose that initiation sites for DNA replication are located between the first intron and exon 7 of the human dnmt1 locus.
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Affiliation(s)
- F D Araujo
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
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23
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Henning KA, Novotny EA, Compton ST, Guan XY, Liu PP, Ashlock MA. Human artificial chromosomes generated by modification of a yeast artificial chromosome containing both human alpha satellite and single-copy DNA sequences. Proc Natl Acad Sci U S A 1999; 96:592-7. [PMID: 9892678 PMCID: PMC15181 DOI: 10.1073/pnas.96.2.592] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A human artificial chromosome (HAC) vector was constructed from a 1-Mb yeast artificial chromosome (YAC) that was selected based on its size from among several YACs identified by screening a randomly chosen subset of the Centre d'Etude du Polymorphisme Humain (CEPH) (Paris) YAC library with a degenerate alpha satellite probe. This YAC, which also included non-alpha satellite DNA, was modified to contain human telomeric DNA and a putative origin of replication from the human beta-globin locus. The resultant HAC vector was introduced into human cells by lipid-mediated DNA transfection, and HACs were identified that bound the active kinetochore protein CENP-E and were mitotically stable in the absence of selection for at least 100 generations. Microdissected HACs used as fluorescence in situ hybridization probes localized to the HAC itself and not to the arms of any endogenous human chromosomes, suggesting that the HAC was not formed by telomere fragmentation. Our ability to manipulate the HAC vector by recombinant genetic methods should allow us to further define the elements necessary for mammalian chromosome function.
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Affiliation(s)
- K A Henning
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
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24
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Balajee AS, May A, Dianova I, Bohr VA. Efficient PCNA complex formation is dependent upon both transcription coupled repair and genome overall repair. Mutat Res 1998; 409:135-46. [PMID: 9875289 DOI: 10.1016/s0921-8777(98)00051-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The protein proliferating cell nuclear antigen (PCNA) is an auxiliary factor for DNA polymerase delta and is involved in the resynthesis step of nucleotide excision repair (NER). After UV irradiation of quiescent cells, PCNA forms an insoluble complex with nuclear substructures. We have investigated associations between NER and its subcomponent pathway, transcription coupled repair (TCR) on PCNA complex formation using genetically related hamster cell lines with different repair characteristics. In DNA repair proficient cells, the PCNA complex was readily detectable within 30 min after UV irradiation by both immunofluorescence and western blot analyses. This complex formation after UV occurs efficiently in quiescent cells. In UV5 (human XP-D homolog) and UV 24 (human XP-B homolog) cells, which are totally deficient in NER, the PCNA complex was not detectable at 30 min after UV. The PCNA complex formation is restored to normal levels in UV5 cells after transfection with the human XPD gene, encoding a subunit of the basal transcription factor, TFIIH. In UV61 (Human CS-B homolog) cells, that are defective only in transcription coupled repair (TCR) of cyclobutane pyrimidine dimers (CPDs), the rate of PCNA complex formation was 2-fold slower than in repair proficient cells. This defect was complemented by transfection of the CSB gene into the UV61 cells. We thus conclude that efficient PCNA complex formation after UV is dependent upon both the NER and TCR pathways in hamster cells. The association of several other DNA repair proteins including XPA, RPA, TFIIH and p53 with the insoluble PCNA complex in UV treated cells suggests a central role for PCNA in different steps of NER.
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Affiliation(s)
- A S Balajee
- Laboratory of Molecular Genetics, National Institute on Aging, NIH, Baltimore, MD 21224, USA
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25
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Kamimura Y, Masumoto H, Sugino A, Araki H. Sld2, which interacts with Dpb11 in Saccharomyces cerevisiae, is required for chromosomal DNA replication. Mol Cell Biol 1998; 18:6102-9. [PMID: 9742127 PMCID: PMC109196 DOI: 10.1128/mcb.18.10.6102] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The DPB11 gene, which genetically interacts with DNA polymerase II (epsilon), one of three replicative DNA polymerases, is required for DNA replication and the S phase checkpoint in Saccharomyces cerevisiae. To identify factors interacting with Dbp11, we have isolated sld (synthetically lethal with dpb11-1) mutations which fall into six complementation groups (sld1 to -6). In this study, we characterized SLD2, encoding an essential 52-kDa protein. High-copy SLD2 suppressed the thermosensitive growth defect caused by dpb11-1. Conversely, high-copy DPB11 suppressed the temperature-sensitive growth defect caused by sld2-6. The interaction between Sld2 and Dpb11 was detected in a two-hybrid assay. This interaction was evident at 25 degreesC but not at 34 degreesC when Sld2-6 or Dpb11-1 replaced its wild-type protein. No interaction between Sld2-6 and Dpb11-1 could be detected even at 25 degreesC. Immunoprecipitation experiments confirmed that Dpb11 physically interacts with Sld2. sld2-6 cells were defective in DNA replication at the restrictive temperature, as were dpb11-1 cells. Further, in dpb11-1 and sld2-6 cells, the bubble-shaped replication intermediates formed in the region of the autonomously replicating sequence reduced quickly after a temperature shift. These results strongly suggest the involvement of the Dpb11-Sld2 complex in a step close to the initiation of DNA replication.
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Affiliation(s)
- Y Kamimura
- Department of Biochemistry and Molecular Biology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871 Japan
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26
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Wegrzyn A, Wegrzyn G. Random inheritance of the replication complex by one of two daughter lambda plasmid copies after a replication round in Escherichia coli. Biochem Biophys Res Commun 1998; 246:634-9. [PMID: 9618264 DOI: 10.1006/bbrc.1998.8711] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There are two pathways for replication of plasmids derived from bacteriophage lambda (so-called lambda plasmids) in Escherichia coli. One pathway is based on the assembly of the new replication complex at ori lambda, and the second requires activity of the replication complex inherited by one of two daughter plasmid copies after each replication round. Although these two replication pathways proceed at the same time in the host cell, we previously found conditions for specific elimination of the pathway based on the assembly of the new replication complex; thus, replication is restricted to that carried out by the heritable replication complex. These conditions are (i) the relaxed response to amino acid starvation and (ii) temperature upshift of the culture of cells harboring the lambda crotsPts1 plasmid. Here we asked whether the replication complex is inherited randomly by one of two daughter plasmid copies or whether the inheritance is preferred by one particular copy, that containing the parental DNA r strand or that bearing the l strand. We performed density shift experiments which allowed us to separate plasmid DNA molecules replicated by the heritable replication complex from those devoid of the replication complex and therefore not able to replicate. Then, [3H]thymidine-labelled plasmid DNA strands were separated and hybridized to membrane-bound ssDNA containing a fragment of either the r or l strand of lambda DNA. We found roughly equal efficiency of hybridization to both r and l strands in all experimental systems used. Therefore, we conclude that the lambda replication complex is randomly inherited by one of two daughter plasmid copies rather than preferentially inherited by either the copy carrying the parental r strand or that containing the l strand.
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Affiliation(s)
- A Wegrzyn
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, University of Gdańsk, Poland.
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27
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Abstract
The cell cycle is driven by the sequential activation of a family of cyclin-dependent kinases (cdk), which phosphorylate and activate proteins that execute events critical to cell cycle progression. In mammalian cells cdk2-cyclin A has a role in S phase. Many replication proteins are potential substrates for this cdk kinase, suggesting that initiation, elongation and checkpoint control of replication could all be regulated by cdk2. The association of PCNA, a replication protein, with cdk-cyclins during G-1 to S phase transition and with cdk-cyclin inhibitors, adds an interesting complexity to regulation of DNA replication.
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Affiliation(s)
- R Fotedar
- Institut de Biologie Structurale J.-P. Ebel, Grenoble, France
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28
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Ishimi Y, Komamura Y, You Z, Kimura H. Biochemical function of mouse minichromosome maintenance 2 protein. J Biol Chem 1998; 273:8369-75. [PMID: 9525946 DOI: 10.1074/jbc.273.14.8369] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Minichromosome maintenance (MCM) proteins play an essential role in eukaryotic DNA replication and bind to chromatin before the initiation of DNA replication. We reported that MCM protein complexes consisting of MCM2, -4, -6, and -7 bind strongly to a histone-Sepharose column (Ishimi, Y., Ichinose, S., Omori, A., Sato, K., and Kimura, H. (1996) J. Biol. Chem. 271, 24115-24122). Here, we have analyzed this interaction at the molecular level. We found that among six mouse MCM proteins, only MCM2 binds to histone; amino acid residues 63-153 are responsible for this binding. The region required for nuclear localization of MCM2 was mapped near this histone-binding domain. Far-Western blotting analysis of truncated forms of H3 histone indicated that amino acid residues 26-67 of H3 histone are required for binding to MCM2. We have also shown that mouse MCM2 can inhibit the DNA helicase activity of the human MCM4, -6, and -7 protein complex. These results suggest that MCM2 plays a different role in the initiation of DNA replication than the other MCM proteins.
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Affiliation(s)
- Y Ishimi
- Mitsubishi Kasei Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194, Japan.
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29
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Orozco BM, Gladfelter HJ, Settlage SB, Eagle PA, Gentry RN, Hanley-Bowdoin L. Multiple cis elements contribute to geminivirus origin function. Virology 1998; 242:346-56. [PMID: 9514968 DOI: 10.1006/viro.1997.9013] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The genome of the geminivirus tomato golden mosaic virus (TGMV) consists of two circular DNA molecules which are dissimilar in sequence except for a highly conserved 200-bp common region that includes the origin for rolling circle replication. To better characterize the plus-strand origin, we analyzed the capacities of various TGMV common region sequences to support episomal replication in tobacco protoplasts when the viral replication proteins AL1 and AL3 were supplied in trans. These experiments demonstrated that the minimal origin is located in 89-bp common region fragment that includes the known AL1 binding motif and a hairpin structure containing the DNA cleavage site. Analyses of mutant origin sequences identified two additional cis elements--one that is required for origin activity and a second that greatly enhances replication. In contrast, a conserved partial copy of the AL1 binding site did not contribute to origin function. Mutational analysis of the functional AL1 binding site showed that both spacing and sequence of this motif are important for replication in vivo and AL1/DNA binding in vitro. Spacing changes between the AL1 binding site and hairpin also negatively impacted TGMV origin function in a position-dependent manner. Together, these results demonstrated that the organization of TGMV plus-strand origin is complex, involving multiple cis elements that are likely to interact with each other during initiation of replication.
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Affiliation(s)
- B M Orozco
- Department of Biochemistry, North Carolina State University, Raleigh 27695-7622, USA.
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30
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Abstract
DNA replication is a complicated process that is largely regulated during stages of initiation. The Siman Virus 40 in vitro replication system has served as an excellent model for studies of the initiation of DNA replication, and its regulation, in eukaryotes. Initiation of SV40 replication requires a single viral protein termed T-antigen, all other proteins are supplied by the host. The recent determination of the solution structure of the T-antigen domain that recognizes the SV40 origin has provided significant insights into the initiation process. For example, it has afforded a clearer understanding of origin recognition, T-antigen oligomerization, and DNA unwinding. Furthermore, the Simian virus 40 in vitro replication system has been used to study nascent DNA formation in the vicinity of the viral origin of replication. Among the conclusions drawn from these experiments is that nascent DNA synthesis does not initiate in the core origin in vitro and that Okazaki fragment formation is complex. These and related studies demonstrate that significant progress has been made in understanding the initiation of DNA synthesis at the molecular level.
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Affiliation(s)
- P A Bullock
- Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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31
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Gladfelter HJ, Eagle PA, Fontes EP, Batts L, Hanley-Bowdoin L. Two domains of the AL1 protein mediate geminivirus origin recognition. Virology 1997; 239:186-97. [PMID: 9426458 DOI: 10.1006/viro.1997.8869] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The geminiviruses tomato golden mosaic virus (TGMV) and bean golden mosaic virus (BGMV) have bipartite genomes. Their A and B DNA components contain cis-acting sequences that function as origins of replication, while their A components encode the trans-acting replication proteins--AL1 and AL3. Earlier experiments demonstrated that virus-specific interactions between the cis- and trans-acting functions are required for TGMV and BGMV replication and that the AL1 proteins of the two viruses specifically bind their respective origins. In the current study, characterization of AL1 and AL3 proteins produced from plant expression cassettes in transient replication assays revealed that interaction between AL1 and the origin is responsible for virus-specific replication. The AL3 protein does not contribute to specificity but can be preferred by its cognate AL1 protein when replication is impaired. Analysis of chimeric proteins showed that two regions of AL1 act as specificity determinants during replication. The first domain is located between amino acids 1 and 116 and recognizes the AL1 origin binding site. The second region, which is between amino acids 121 and 209, is not dependent on the known AL1 DNA binding site. Analysis of wild type and chimeric proteins in transient transcription assays showed that AL1 also represses its own promoter in a virus-specific manner. Transcriptional specificity is conferred primarily by AL1 amino acids 1-93 with amino acids 121-209 making a smaller contribution. Together, these results demonstrated that the virus-specific interactions of AL1 during replication and transcription are complex, involving at least two discreet domains of the protein.
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Affiliation(s)
- H J Gladfelter
- Department of Biochemistry, North Carolina State University, Raleigh 27695-7622, USA
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32
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Toone WM, Aerne BL, Morgan BA, Johnston LH. Getting started: regulating the initiation of DNA replication in yeast. Annu Rev Microbiol 1997; 51:125-49. [PMID: 9343346 DOI: 10.1146/annurev.micro.51.1.125] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Initiation of DNA replication in yeast appears to operate through a two-step process. The first step occurs at the end of mitosis in the previous cell cycle, where, following the decrease in B cyclin-dependent kinase activity, an extended protein complex called the prereplicative complex (pre-RC) forms over the origin of replication. This complex is dependent on the association of the Cdc6 protein with the Origin Recognition Complex (ORC) and appears concomitantly with the nuclear entry of members of the Mcm family of proteins. The second step is dependent upon the cell passing through a G1 decision point called Start. If the environmental conditions are favorable, and the cells reach a critical size, then there is a rise in G1 cyclin-dependent kinase activity, which leads to the activation of downstream protein kinases; the protein kinases are, in turn, required for triggering initiation from the preformed initiation complexes. These protein kinases, Dbf4-Cdc7 and Clb5/6(B-cyclin)-Cdc28, are thought to phosphorylate targets within the pre-RC. The subsequent rise in B cyclin protein kinase activity following Start not only triggers origin firing, but also inhibits the formation of new pre-RCs, which ensures that there is only one S phase in each cell cycle. The destruction of B-cyclin protein kinase activity at the end of the cell cycle potentiates the formation of new pre-RCs-resetting origins for the next S phase.
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Affiliation(s)
- W M Toone
- Division of Yeast Genetics, National Institute for Medical Research, Mill Hill, London, UK
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33
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Aleksenko A, Clutterbuck AJ. Autonomous plasmid replication in Aspergillus nidulans: AMA1 and MATE elements. Fungal Genet Biol 1997; 21:373-87. [PMID: 9290250 DOI: 10.1006/fgbi.1997.0980] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
With few exceptions, in eukaryotic organisms the presence of a chromosomal replicator on a circular vector molecule is not sufficient to confer on it the ability to persist and replicate extrachromosomally. However, it is possible to isolate from genomes of some filamentous fungi DNA fragments which can provide extrachromosomal maintenance of plasmids. In Aspergillus nidulans, two functional classes of such sequences can be distinguished: effective plasmid replicators (e.g., AMA1) and transformation enhancers (e.g., ANS1 or MATEs), which apparently are able to initiate aberrant replication, leading to vector rearrangement and multimerization and eventually resulting in chromosomal integration. We discuss the similarity of these events to DNA amplification in other eukaryotes. A model is suggested which accounts for the formation of effective replicating plasmids as a result of sequence amplification. The model is based on the observation that in some organisms, including A. nidulans and Schizosaccharomyces pombe, duplication of an inefficient replicator enhances its efficiency dramatically. Some structural traits of transformation enhancers in A. nidulans imply a role for topoisomerases in amplification and replication of circular DNA molecules. We discuss practical applications of replicative vectors for gene cloning and expression studies.
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Affiliation(s)
- A Aleksenko
- Institute of Genetics and Selection of Industrial Microorganisms, Moscow, Russia
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34
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Hardy CF, Dryga O, Seematter S, Pahl PM, Sclafani RA. mcm5/cdc46-bob1 bypasses the requirement for the S phase activator Cdc7p. Proc Natl Acad Sci U S A 1997; 94:3151-5. [PMID: 9096361 PMCID: PMC20337 DOI: 10.1073/pnas.94.7.3151] [Citation(s) in RCA: 211] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/1996] [Accepted: 01/27/1997] [Indexed: 02/04/2023] Open
Abstract
Cdc7p is a protein kinase that is required for G1/S transition and initiation of DNA replication in Saccharomyces cerevisiae. The mechanisms whereby Cdc7p and its substrates exerts their effects are unknown. We report here the characterization in S. cerevisiae of a recessive mutation in a member of the MCM family, MCM5/CDC46, which bypasses the requirement for Cdc7p and its interacting factor Dbf4p. Because the MCM family of evolutionarily conserved proteins have been implicated in restricting DNA replication to once per cell cycle, our studies suggest that Cdc7p is required late in G1 because in its absence the Mcm5p/Cdc46p blocks the initiation of DNA replication. Moreover, Mcm5p/Cdc46p may have both positive and negative effects on the ability of cell to initiate replication.
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Affiliation(s)
- C F Hardy
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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35
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Cannella D, Roberts JM, Fotedar R. Association of cyclin A and cdk2 with SV40 DNA in replication initiation complexes is cell cycle dependent. Chromosoma 1997; 105:349-59. [PMID: 9087377 DOI: 10.1007/bf02529750] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The cell cycle is driven by the sequential activation of a family of cyclin-dependent kinases (CDK) in association with cyclins. In mammalian cells the timing of activation of cyclin A-associated kinase activity coincides with the onset of DNA synthesis in S-phase. Using in vitro replication of SV40 origin-containing DNA as a model system, we have analyzed the proteins associated with DNA during initiation of DNA replication in S-phase cell extracts. This analysis reveals that, in addition to replication initiation proteins, cyclin A and cdk2 are also specifically associated with DNA. The association of cyclin A and cdk2 with DNA during initiation is cell cycle regulated and occurs specifically in the presence of SV40 origin-containing plasmid and SV40 T antigen (the viral replication initiator protein). The interactions among proteins involved in initiation play an important role in DNA replication. We therefore investigated the ability of cyclin A and cdk2 to associate with replication initiation proteins. Under replication initiation conditions, cyclin A and cdk2 from S-phase extracts specifically associate with SV40 T antigen. Further, the interaction of cyclin A-cdk2 with SV40 T antigen is mediated via cyclin A, and purified recombinant cyclin A associates directly with SV40 T antigen. Taken together, our results suggest that cyclin A and cdk2 are components of the SV40 replication initiation complex, and that protein-protein interactions between cyclin A-cdk2 and T antigen may facilitate the association of cyclin A-cdk2 with the complex.
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Affiliation(s)
- D Cannella
- Institut de Biologie Structurale J.-P. Ebel, 41 Avenue des Martyrs, F-38027 Grenoble, Cedex 1, France
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36
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Abstract
Recent structural studies of the Epstein-Barr virus EBNA1 protein bound to DNA suggest that it binds to DNA replication origins in a two-step process; the first step involves recognition of the correct sequence and the second initiates structural changes in the DNA.
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Affiliation(s)
- F B Dean
- Microbiology Department, Hearst Research Foundation and Howard Hughes Medical Institute, Cornell University Medical College, 1300 York Avenue, New York, New York 10021, USA
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37
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Bochkarev A, Barwell JA, Pfuetzner RA, Bochkareva E, Frappier L, Edwards AM. Crystal structure of the DNA-binding domain of the Epstein-Barr virus origin-binding protein, EBNA1, bound to DNA. Cell 1996; 84:791-800. [PMID: 8625416 DOI: 10.1016/s0092-8674(00)81056-9] [Citation(s) in RCA: 174] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The Epstein-Barr virus nuclear antigen 1 (EBNA1) protein binds to and activates DNA replication from oriP, the latent origin of DNA replication in Epstein-Barr virus. The crystal structure of the DNA-binding domain of EBNA1 bound to an 18 bp binding site was solved at 2.4 A resolution. EBNA1 comprises two domains, a flanking and a core domain. The flanking domain, which includes a helix that projects into the major groove and an extended chain that travels along the minor groove, makes all of the sequence-determining contacts with the DNA. The core domain, which is structurally homologous to the complete DNA-binding domain of the bovine papilloma virus E2 protein, makes no direct contacts with the DNA bases. A model for origin unwinding is proposed that incorporates the known biochemical and structural features of the EBNA1-origin interaction.
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Affiliation(s)
- A Bochkarev
- Institute for Molecular Biology and Biotechnology, Cancer Research Group, Department of Pathology, McMaster University, Hamilton, Ontario Canada
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38
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Kearsey SE, Maiorano D, Holmes EC, Todorov IT. The role of MCM proteins in the cell cycle control of genome duplication. Bioessays 1996; 18:183-90. [PMID: 8867732 DOI: 10.1002/bies.950180305] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The regulatory mechanism which ensures that eukaryotic chromosomes replicate precisely once per cell cycle is a basic and essential cellular property of eukaryotes. This fundamental aspect of DNA replication is still poorly understood, but recent advances encourage the view that we may soon have a clearer picture of how this regulation is achieved. This review will discuss in particular the role of proteins in the minichromosome maintenance (MCM) family, which may hold the key to understanding how DNA is replicated once, and only once, per cell cycle.
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Affiliation(s)
- S E Kearsey
- Department of Zoology, University of Oxford, England.
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39
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Li R, Hannon GJ, Beach D, Stillman B. Subcellular distribution of p21 and PCNA in normal and repair-deficient cells following DNA damage. Curr Biol 1996; 6:189-99. [PMID: 8673466 DOI: 10.1016/s0960-9822(02)00452-9] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND The p21 protein binds to both cyclin-dependent kinases (Cdks) and the proliferating cell nuclear antigen (PCNA). In mammalian cells, DNA damage results in an increase in the level of p53 protein, which stimulates expression of the gene encoding p21, which in turn leads to an inhibition of Cdk activity. Biochemical studies have shown that the direct interaction between p21 and PCNA blocks the latter's function in DNA replication but not in DNA repair. In addition to the p53-dependent damage response, the stimulation of quiescent cells with serum can also cause a p53-independent elevation in p21 gene expression. It is not clear, however, whether the induction of p21 protein under these two circumstances serves the same purpose. In this study, we have investigated the kinetics of p21 induction by DNA damage and serum stimulation and the consequent effects on cell-cycle progression. Using both normal and repair-deficient human cells, we have also analyzed the nuclear distribution of p21 in relation to that of PCNA. RESULTS In vivo immunofluorescence staining experiments indicate that, following UV damage, DNA repair is not inhibited by the presence of a large amount of p21 protein in the nucleus; in contrast, cells undergoing DNA replication during S phase contain very low amounts of p21. The addition of serum induced a transitory elevation of p21 levels, whereas UV damage to cells resulted in a sustained, high level of p21 that was more tightly associated with the nuclear structure. Interestingly, cells deficient in global nucleotide excision-repair displayed a distinct pattern of detergent-insoluble p21 that co-localized with PCNA. CONCLUSIONS The in vivo studies presented here, which are consistent with our previous findings in vitro, indicate that p21 has a differential effect on DNA replication and DNA repair, and that the induction of p21 by serum and DNA damage may have different consequences. Furthermore, the co-localization of p21 and PCNA in the nucleus of normal and repair-deficient human cells indicates that p21 and PCNA interact during post-damage events.
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Affiliation(s)
- R Li
- Cold Spring Harbor Laboratory, New York 11724, USA
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40
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Abstract
The genome of the geminivirus tomato golden mosaic virus (TGMV) consists of two single-stranded circular DNAs, A and B, that replicate through a rolling-circle mechanism in nuclei of infected plant cells. The TGMV origin of replication is located in a conserved 5' intergenic region and includes at least two functional elements: the origin recognition site of the essential viral replication protein, AL1, and a sequence motif with the potential to form a hairpin or cruciform structure. To address the role of the hairpin motif during TGMV replication, we constructed a series of B-component mutants that resolved sequence changes from structural alterations of the motif. Only those mutant B DNAs that retained the capacity to form the hairpin structure replicated to wild-type levels in tobacco protoplasts when the viral replication proteins were provided in trans from a plant expression cassette. In contrast, the same B DNAs replicated to significantly lower levels in transient assays that included replicating, wild-type TGMV A DNA. These data established that the hairpin structure is essential for TGMV replication, whereas its sequence affects the efficiency of replication. We also showed that TGMV AL1 functions as a site-specific endonuclease in vitro and mapped the cleavage site to the loop of the hairpin. In vitro cleavage analysis of two TGMV B mutants with different replication phenotypes indicated that there is a correlation between the two assays for origin activity. These results suggest that the in vivo replication results may reflect structural and sequence requirements for DNA cleavage during initiation of rolling-circle replication.
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Affiliation(s)
- B M Orozco
- Department of Biochemistry, North Carolina State University, Raleigh 27695-7622, USA
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41
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Dahmann C, Diffley JF, Nasmyth KA. S-phase-promoting cyclin-dependent kinases prevent re-replication by inhibiting the transition of replication origins to a pre-replicative state. Curr Biol 1995; 5:1257-69. [PMID: 8574583 DOI: 10.1016/s0960-9822(95)00252-1] [Citation(s) in RCA: 310] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND DNA replication and mitosis are triggered by activation of kinase complexes, each made up of a cyclin and a cyclin-dependent kinase (Cdk). It had seemed possible that the association of Cdks with different classes of cyclins specifies whether S phase (replication) or M phase (mitosis) will occur. The recent finding that individual B-type cyclins (encoded by the genes CLB1-CLB6) can have functions in both processes in the budding yeast Saccharomyces cerevisiae casts doubt on this notion. RESULTS S. cerevisiae strains lacking C1b1-C1b4 undergo DNA replication once but fail to enter mitosis. We have isolated mutations in two genes, SIM1 and SIM2 (SIM2 is identical to SEC72), which allow such cells to undergo an extra round of DNA replication without mitosis. The Clb5 kinase, which promotes S phase, remains active during the G2-phase arrest of cells of the parental strain, but its activity declines rapidly in sim mutants. Increased expression of the CLB5 gene prevents re-replication. Thus, a cyclin B-kinase that promotes DNA replication in G1-phase cells can prevent re-replication in G2-phase cells. Inactivation of C1b kinases by expression of the specific C1b-Cdk1 inhibitor p40SIC1 is sufficient to induce a prereplicative state at origins of replication in cells blocked in G2/M phase by nocodazole. Re-activation of C1b-Cdk1 kinases induces a second round of DNA replication. CONCLUSIONS We propose that S-phase-promoting cyclin B--Cdk complexes prevent re-replication during S, G2 and M phases by inhibiting the transition of replication origins to a pre-replicative state. This model can explain both why origins 'fire' only once per S phase and why S phase is dependent on completion of the preceding M phase.
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Affiliation(s)
- C Dahmann
- I.M.P. Research Institute of Molecular Pathology, Vienna, Austria
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42
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Barwell JA, Bochkarev A, Pfuetzner RA, Tong H, Yang DS, Frappier L, Edwards AM. Overexpression, purification, and crystallization of the DNA binding and dimerization domains of the Epstein-Barr virus nuclear antigen 1. J Biol Chem 1995; 270:20556-9. [PMID: 7657632 DOI: 10.1074/jbc.270.35.20556] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The Epstein-Barr virus nuclear antigen (EBNA) 1 binds to and activates DNA replication from the latent origin of Epstein-Barr virus. Six different fragments of EBNA1 that retain DNA binding activity were expressed in bacteria, purified, and crystallized. Two fragments, EBNA470-619 and EBNA470-607, formed well ordered crystals that diffracted beyond 2.5-A resolution. Two different EBNA470-619 crystals were grown from sodium formate, pH 6-6.5. One crystal belonged to the trigonal space group P3 with unit cell dimensions a = b = 86.5 A and c = 31.8 A and with two molecules in the asymmetric unit. The other crystal, which appeared only twice and was likely related to the P3 crystal form, belonged to the trigonal space group P312 with cell dimensions a = b = 86.7 A and c = 31.8 A. Crystals of EBNA470-607 were grown by lowering the salt concentration to 0-100 mM NaCl at pH 6.0. These crystals belonged to the orthorhombic space group P2(1)2(1)2(1) and had cell dimensions a = 59 A, b = 66.9 A, and c = 69.8 A with two molecules in the asymmetric unit.
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Affiliation(s)
- J A Barwell
- Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario, Canada
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43
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Liang C, Weinreich M, Stillman B. ORC and Cdc6p interact and determine the frequency of initiation of DNA replication in the genome. Cell 1995; 81:667-76. [PMID: 7774008 DOI: 10.1016/0092-8674(95)90528-6] [Citation(s) in RCA: 286] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The origin recognition complex (ORC) binds replicators in the yeast S. cerevisiae in a manner consistent with it being an initiator protein for DNA replication. Two-dimensional (2D) gel techniques were used to examine directly initiation of chromosomal DNA replication in temperature-sensitive orc mutants. Unlike in wild-type cells, in orc2-1 and orc5-1 mutant cells, only a subset of replicators formed active origins of DNA replication at the permissive temperature. At the restrictive temperature, the number of active replicators was diminished further. Using a genetic screen, CDC6 was identified as a multicopy suppressor of orc5-1. 2D gel and biochemical analyses demonstrated that Cdc6p interacted functionally and physically with ORC. We suggest that ORC and Cdc6p form a prereplication complex at individual replicators and therefore cooperate to determine the frequency of initiation of DNA replication in the genome.
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Affiliation(s)
- C Liang
- Cold Spring Harbor Laboratory, New York 11724, USA
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44
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Nahreini P, Mathews MB. Effects of the simian virus 40 origin of replication on transcription from the human immunodeficiency virus type 1 promoter. J Virol 1995; 69:1296-301. [PMID: 7815509 PMCID: PMC188708 DOI: 10.1128/jvi.69.2.1296-1301.1995] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Positive and negative effects of DNA replication on gene transcription have been documented in a variety of systems. We examined the effects of the simian virus 40 (SV40) origin of replication on transcription from the human immunodeficiency virus type 1 (HIV-1) promoter, using a transient expression assay in COS-1 cells. The basal activity and Tat transactivation of the HIV promoter were greatly stimulated by the SV40 origin of replication independent of its position relative to the long terminal repeat. These effects were abolished by mutational inactivation of the SV40 origin and were reduced by a DNA replication inhibitor. The magnitude of promoter activation exceeded the increment expected from the increase in template number resulting from DNA replication. The SV40 T-antigen-induced DNA replication augmented the generation of both processive and nonprocessive HIV long terminal repeat-directed transcripts, and Tat primarily enhanced the initiation of those transcripts that were destined to be efficiently elongated. Our data suggest that the HIV promoter displays greater transcriptional activity on replicative DNA templates. This property may influence the activity of integrated HIV provirus and its transition from latency to productive infection.
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Affiliation(s)
- P Nahreini
- Cold Spring Harbor Laboratory, New York 11724
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45
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Bambara RA, Huang L. Reconstitution of mammalian DNA replication. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1995; 51:93-122. [PMID: 7659780 DOI: 10.1016/s0079-6603(08)60877-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- R A Bambara
- Department of Biochemistry, University of Rochester School of Medicine and Dentistry, New York 14642, USA
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46
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Affiliation(s)
- B Stillman
- Cold Spring Harbor Laboratory, New York 11724
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