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Bianco PR, Lu Y. Single-molecule insight into stalled replication fork rescue in Escherichia coli. Nucleic Acids Res 2021; 49:4220-4238. [PMID: 33744948 PMCID: PMC8096234 DOI: 10.1093/nar/gkab142] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/15/2021] [Accepted: 02/22/2021] [Indexed: 01/05/2023] Open
Abstract
DNA replication forks stall at least once per cell cycle in Escherichia coli. DNA replication must be restarted if the cell is to survive. Restart is a multi-step process requiring the sequential action of several proteins whose actions are dictated by the nature of the impediment to fork progression. When fork progress is impeded, the sequential actions of SSB, RecG and the RuvABC complex are required for rescue. In contrast, when a template discontinuity results in the forked DNA breaking apart, the actions of the RecBCD pathway enzymes are required to resurrect the fork so that replication can resume. In this review, we focus primarily on the significant insight gained from single-molecule studies of individual proteins, protein complexes, and also, partially reconstituted regression and RecBCD pathways. This insight is related to the bulk-phase biochemical data to provide a comprehensive review of each protein or protein complex as it relates to stalled DNA replication fork rescue.
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Affiliation(s)
- Piero R Bianco
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
| | - Yue Lu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA
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2
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Abstract
Proteins of the Rad51 family play a key role in homologous recombination by carrying out DNA strand exchange. Here, we present the methodology and the protocols for the 4-strand exchange between gapped circular DNA and homologous linear duplex DNA promoted by human Rad51 and Escherichia coli RecA orthologs. This reaction includes formation of joint molecules and their extension by branch migration in a polar manner. The presented methodology may be used for reconstitution of the medial-to-late stages of homologous recombination in vitro as well as for investigation of the mechanisms of branch migration by helicase-like proteins, e.g., Rad54, BLM, or RecQ1.
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Profile of Stephen C. West. Proc Natl Acad Sci U S A 2017; 114:7738-7740. [DOI: 10.1073/pnas.1710706114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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4
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Guo C, Li G, Liu Z, Sun L, Sun Y, Xu F, Zhang Y, Yang T, Li Z. Influence of Polyelectrolyte on DNA-RecA Nucleoprotein Filaments: Poly-L-Lysine Used as a Model. Chemphyschem 2009; 10:1624-9. [DOI: 10.1002/cphc.200800850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Abstract
The bacterial RecA protein participates in a remarkably diverse set of functions, all of which are involved in the maintenance of genomic integrity. RecA is a central component in both the catalysis of recombinational DNA repair and the regulation of the cellular SOS response. Despite the mechanistic differences of its functions, all require formation of an active RecA/ATP/DNA complex. RecA is a classic allosterically regulated enzyme, and ATP binding results in a dramatic increase in DNA binding affinity and a cooperative assembly of RecA subunits to form an ordered, helical nucleoprotein filament. The molecular events that underlie this ATP-induced structural transition are becoming increasingly clear. This review focuses on descriptions of our current understanding of the molecular design and allosteric regulation of RecA. We present a comprehensive list of all published recA mutants and use the results of various genetic and biochemical studies, together with available structural information, to develop ideas regarding the design of RecA functional domains and their catalytic organization.
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Affiliation(s)
- Dharia A McGrew
- Department of Biochemistry and Molecular Pharmacology, Aaron Lazare Research Building, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA
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7
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Chan YH, Wong JTY. Concentration-dependent organization of DNA by the dinoflagellate histone-like protein HCc3. Nucleic Acids Res 2007; 35:2573-83. [PMID: 17412706 PMCID: PMC1885672 DOI: 10.1093/nar/gkm165] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The liquid crystalline chromosomes of dinoflagellates are the alternative to the nucleosome-based organization of chromosomes in the eukaryotes. These nucleosome-less chromosomes have to devise novel ways to maintain active parts of the genome. The dinoflagellate histone-like protein HCc3 has significant sequence identity with the bacterial DNA-binding protein HU. HCc3 also has a secondary structure resembling HU in silico. We have examined HCc3 in its recombinant form. Experiments on DNA-cellulose revealed its DNA-binding activity is on the C-terminal domain. The N-terminal domain is responsible for intermolecular oligomerization as demonstrated by cross-linking studies. However, HCc3 could not complement Escherichia coli HU-deficient mutants, suggesting functional differences. In ligation assays, HCc3-induced DNA concatenation but not ring closure as the DNA-bending HU does. The basic HCc3 was an efficient DNA condensing agent, but it did not behave like an ordinary polycationic compound. HCc3 also induced specific structures with DNA in a concentration-dependent manner, as demonstrated by atomic force microscopy (AFM). At moderate concentration of HCc3, DNA bridging and bundling were observed; at high concentrations, the complexes were even more condensed. These results are consistent with a biophysical role for HCc3 in maintaining extended DNA loops at the periphery of liquid crystalline chromosomes.
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Affiliation(s)
| | - Joseph T. Y. Wong
- *To whom correspondence should be addressed +86-852-2358-7343+86-852-2358-1559
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8
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Shigemori Y, Mikawa T, Shibata T, Oishi M. Multiplex PCR: use of heat-stable Thermus thermophilus RecA protein to minimize non-specific PCR products. Nucleic Acids Res 2005; 33:e126. [PMID: 16087733 PMCID: PMC1183492 DOI: 10.1093/nar/gni111] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In this paper we report that the inclusion of heat-resistant RecA protein from a thermophilic bacteria, Thermus thermophilus, and its cofactor (ATP) in PCR effectively eliminates non-specific PCR products. The effect of RecA protein, which catalyzes pairing between homologous DNA molecules with great fidelity in genetic recombination, is due to its promotion of precise priming in PCR (i.e. priming at sites where the primer sequence is completely complementary to that of the target sequence). In addition, the RecA protein substantially reduces the primer concentration required for PCR. These experimental results have led to the realization of multiplex PCR, which involves PCR for multiple sites in the same reaction mixture. We were able to successfully perform multiplex PCR with over a dozen reactions without affecting the amplification pattern of the PCR products.
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Affiliation(s)
- Yasushi Shigemori
- Kazusa DNA Research Institute2-6-7 Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan
- Aisin Cosmos R&D Co., Ltd2-6-7 Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan
| | - Tsutomu Mikawa
- RIKEN Harima Institute/SPring-8Mikazuki cho, Hyogo 679-5148, Japan
- RIKEN Discovery Research Institute2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Takehiko Shibata
- RIKEN Discovery Research Institute2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Michio Oishi
- Kazusa DNA Research Institute2-6-7 Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan
- To whom correspondence should be addressed. Tel: +81 438 52 3945; Fax: +81 438 52 3946;
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9
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Sattin BD, Goh MC. Direct observation of the assembly of RecA/DNA complexes by atomic force microscopy. Biophys J 2004; 87:3430-6. [PMID: 15315951 PMCID: PMC1304809 DOI: 10.1529/biophysj.104.045567] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The formation of the RecA/DNA nucleofilament on nicked circular double stranded (ds) DNA in the presence of ATPgammaS was studied using the atomic force microscope (AFM) at nanometer resolution. The AFM allowed simultaneous observation of both dsDNA substrate and RecA protein-coated sections such that they are highly distinguishable. Using a time series of images, the complex formation was monitored. AFM imaging provided direct evidence that assembly of the nucleofilaments occurs via a nucleation and growth mechanism. The nucleation step is much slower than the growth phase, as demonstrated by the predominance of naked dsDNA at early and middle time points, followed by the rapid appearance of partially then fully formed complexes. Observation of the formation of nucleation sites without accompanying growth on unnicked dsDNA enabled an estimate of the nucleation rate, of 5 x 10(-5) RecA min(-1) bp(-1). The published model for the analysis of RecA assembly on dsDNA deduces a single kinetic parameter that prevents the separate determination of nucleation rate and growth rate. By directly measuring the nucleation rate with the AFM, this model is employed to determine a growth rate of 202 min(-1). These AFM results provide the first direct evidence of previous results on complex formation obtained only by indirect means.
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Affiliation(s)
- Bernie D Sattin
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
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Abstract
An 8,000-molecular-weight (8K) T antigen was found in all cells transformed by simian virus 40. The 8K T antigen was weakly labeled in vivo with [35S]methionine or 32Pi. A deletion in the human papovavirus BK genome, in the region coding for the carboxy-terminal end of the large T antigen, reduced the size of the 8K T antigen. The last 80 amino acids of the large T antigen include the sequence Asp-Asp-Asp-Asp unique to the activation peptide of trypsinogen. Large T antigen bound diisopropyl fluorophosphate and was retained by D-phenylalanine coupled to Sepharose beads, an affinity adsorbent that can retain chymotrypsin. The large T antigen and the recA protein of Escherichia coli, a known protease, have several properties in common as well as several similar sequences. Antibodies against large T antigen interacted with native recA protein.
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Abstract
An 8,000-molecular-weight (8K) T antigen was found in all cells transformed by simian virus 40. The 8K T antigen was weakly labeled in vivo with [35S]methionine or 32Pi. A deletion in the human papovavirus BK genome, in the region coding for the carboxy-terminal end of the large T antigen, reduced the size of the 8K T antigen. The last 80 amino acids of the large T antigen include the sequence Asp-Asp-Asp-Asp unique to the activation peptide of trypsinogen. Large T antigen bound diisopropyl fluorophosphate and was retained by D-phenylalanine coupled to Sepharose beads, an affinity adsorbent that can retain chymotrypsin. The large T antigen and the recA protein of Escherichia coli, a known protease, have several properties in common as well as several similar sequences. Antibodies against large T antigen interacted with native recA protein.
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Affiliation(s)
- R Seif
- Laboratoire d'Enzymologie, Centre National de la Recherche Scientifique, 91190 Gif-sur-Yvette, France
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12
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Singleton SF, Simonette RA, Sharma NC, Roca AI. Intein-mediated affinity-fusion purification of the Escherichia coli RecA protein. Protein Expr Purif 2002; 26:476-88. [PMID: 12460773 DOI: 10.1016/s1046-5928(02)00571-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The RecA protein of Escherichia coli plays important roles in homologous recombination, recombinational DNA repair, and SOS induction. Because its functions are conserved among the phylogenetic kingdoms, RecA investigations have provided a paradigm for understanding these biological processes. The RecA protein has been overproduced in E. coli and purified using a variety of purification schemes requiring multiple, time-intensive steps. The purification schemes share a dependence on appropriate RecA structure and/or function at one or more steps. In this report, we used a modified protein splicing element (intein) and a chitin-binding domain, fused to the C-terminus of RecA, to facilitate a one-step affinity purification of RecA protein without modification of the native protein sequence. Following the single chromatographic step, RecA protein that is greater than 95% physical purity at a concentration of greater than microM was obtained. The protein displays in vitro activities that are identical to those of protein isolated using classical procedures. The purification strategy described here promises to yield mutant RecA proteins in sufficient quantity for rigorous biophysical characterization without dependence on intrinsic RecA function.
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Affiliation(s)
- Scott F Singleton
- Department of Chemistry, Rice University, P.O. Box 1892 MS 65, Houston, TX 77251-1892, USA.
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13
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Shibata T, Nishinaka T, Mikawa T, Aihara H, Kurumizaka H, Yokoyama S, Ito Y. Homologous genetic recombination as an intrinsic dynamic property of a DNA structure induced by RecA/Rad51-family proteins: a possible advantage of DNA over RNA as genomic material. Proc Natl Acad Sci U S A 2001; 98:8425-32. [PMID: 11459985 PMCID: PMC37453 DOI: 10.1073/pnas.111005198] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Heteroduplex joints are general intermediates of homologous genetic recombination in DNA genomes. A heteroduplex joint is formed between a single-stranded region (or tail), derived from a cleaved parental double-stranded DNA, and homologous regions in another parental double-stranded DNA, in a reaction mediated by the RecA/Rad51-family of proteins. In this reaction, a RecA/Rad51-family protein first forms a filamentous complex with the single-stranded DNA, and then interacts with the double-stranded DNA in a search for homology. Studies of the three-dimensional structures of single-stranded DNA bound either to Escherichia coli RecA or Saccharomyces cerevisiae Rad51 have revealed a novel extended DNA structure. This structure contains a hydrophobic interaction between the 2' methylene moiety of each deoxyribose and the aromatic ring of the following base, which allows bases to rotate horizontally through the interconversion of sugar puckers. This base rotation explains the mechanism of the homology search and base-pair switch between double-stranded and single-stranded DNA during the formation of heteroduplex joints. The pivotal role of the 2' methylene-base interaction in the heteroduplex joint formation is supported by comparing the recombination of RNA genomes with that of DNA genomes. Some simple organisms with DNA genomes induce homologous recombination when they encounter conditions that are unfavorable for their survival. The extended DNA structure confers a dynamic property on the otherwise chemically and genetically stable double-stranded DNA, enabling gene segment rearrangements without disturbing the coding frame (i.e., protein-segment shuffling). These properties may give an extensive evolutionary advantage to DNA.
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Affiliation(s)
- T Shibata
- Cellular and Molecular Biology Laboratory, RIKEN, The Institute of Physical and Chemical Research, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan.
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14
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Cox MM. Historical overview: searching for replication help in all of the rec places. Proc Natl Acad Sci U S A 2001; 98:8173-80. [PMID: 11459950 PMCID: PMC37418 DOI: 10.1073/pnas.131004998] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
For several decades, research into the mechanisms of genetic recombination proceeded without a complete understanding of its cellular function or its place in DNA metabolism. Many lines of research recently have coalesced to reveal a thorough integration of most aspects of DNA metabolism, including recombination. In bacteria, the primary function of homologous genetic recombination is the repair of stalled or collapsed replication forks. Recombinational DNA repair of replication forks is a surprisingly common process, even under normal growth conditions. The new results feature multiple pathways for repair and the involvement of many enzymatic systems. The long-recognized integration of replication and recombination in the DNA metabolism of bacteriophage T4 has moved into the spotlight with its clear mechanistic precedents. In eukaryotes, a similar integration of replication and recombination is seen in meiotic recombination as well as in the repair of replication forks and double-strand breaks generated by environmental abuse. Basic mechanisms for replication fork repair can now inform continued research into other aspects of recombination. This overview attempts to trace the history of the search for recombination function in bacteria and their bacteriophages, as well as some of the parallel paths taken in eukaryotic recombination research.
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Affiliation(s)
- M M Cox
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706-1544, USA.
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15
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Abstract
A double-strand break in genomic DNA that remains unrepaired can be lethal for a cell. Indeed, the integrity of the genome is paramount for survival. It is therefore surprising that some cells deliberately introduce double-strand breaks at certain times during their life cycle. Why might they do this? What are the benefits? How are these breaks repaired? The answers to these questions lie in understanding the basis of meiotic recombination, the process that leads to genetic variation. This review summarizes the key roles played by the two recombinases, Dmc1 and Rad51, in the faithful repair of DNA breaks.
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Affiliation(s)
- J Y Masson
- Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, EN6 3LD, Herts, UK
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Aihara H, Ito Y, Kurumizaka H, Yokoyama S, Shibata T. The N-terminal domain of the human Rad51 protein binds DNA: structure and a DNA binding surface as revealed by NMR. J Mol Biol 1999; 290:495-504. [PMID: 10390347 DOI: 10.1006/jmbi.1999.2904] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Human Rad51 protein (HsRad51) is a homolog of Escherichia coli RecA protein, and functions in DNA repair and recombination. In higher eukaryotes, Rad51 protein is essential for cell viability. The N-terminal region of HsRad51 is highly conserved among eukaryotic Rad51 proteins but is absent from RecA, suggesting a Rad51-specific function for this region. Here, we have determined the structure of the N-terminal part of HsRad51 by NMR spectroscopy. The N-terminal region forms a compact domain consisting of five short helices, which shares structural similarity with a domain of endonuclease III, a DNA repair enzyme of E. coli. NMR experiments did not support the involvement of the N-terminal domain in HsRad51-HsBrca2 interaction or the self-association of HsRad51 as proposed by previous studies. However, NMR tiration experiments demonstrated a physical interaction of the domain with DNA, and allowed mapping of the DNA binding surface. Mutation analysis showed that the DNA binding surface is essential for double-stranded and single-stranded DNA binding of HsRad51. Our results suggest the presence of a DNA binding site on the outside surface of the HsRad51 filament and provide a possible explanation for the regulation of DNA binding by phosphorylation within the N-terminal domain.
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Affiliation(s)
- H Aihara
- Cellular & Molecular Biology Laboratory, The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
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Shivashankar GV, Feingold M, Krichevsky O, Libchaber A. RecA polymerization on double-stranded DNA by using single-molecule manipulation: the role of ATP hydrolysis. Proc Natl Acad Sci U S A 1999; 96:7916-21. [PMID: 10393922 PMCID: PMC22162 DOI: 10.1073/pnas.96.14.7916] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The polymerization of RecA on individual double-stranded DNA molecules is studied. A linear DNA (lambda DNA, 48.5 Kb), anchored at one end to a cover glass and at the other end to an optically trapped 3-micrometers diameter polystyrene bead, serves as a template. The elongation caused by RecA assembly is measured in the presence of ATP and ATP[gammaS]. By using force extension and hydrodynamic recoil, a value of the persistence length of the RecA-DNA complex is obtained. In the presence of ATP, the polymer length is unstable, first growing to saturation and then decreasing. This suggests a transient dynamics of association and dissociation for RecA on a double-stranded DNA, the process being controlled by ATP hydrolysis. Part of this dynamics is suppressed in the presence of ATP[gammaS], leading to a stabilized RecA-DNA complex. A one-dimensional nucleation and growth model is presented that may account for the protein assembly.
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Affiliation(s)
- G V Shivashankar
- Center for Studies in Physics and Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
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18
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Biet E, Sun J, Dutreix M. Conserved sequence preference in DNA binding among recombination proteins: an effect of ssDNA secondary structure. Nucleic Acids Res 1999; 27:596-600. [PMID: 9862985 PMCID: PMC148220 DOI: 10.1093/nar/27.2.596] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Repetitive sequences have been proposed to be recombinogenic elements in eukaryotic chromosomes. We tested whether dinucleotide repeats sequences are preferential sites for recombination because of their high affinity for recombination enzymes. We compared the kinetics of the binding of the scRad51, hsRad51 and ecRecA proteins to oligonucleotides with repeats of dinucleotides GT, CA, CT, GA, GC or AT. Since secondary structures in single-stranded DNA (ssDNA) act as a barrier to complete binding we measured whether these oligonucleotides are able to form stable secondary structures. We show that the preferential binding of recombination proteins is conserved among the three proteins and is influenced mainly by secondary structures in ssDNA.
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Affiliation(s)
- E Biet
- Institut Curie, Section de Recherche UMR144-CNRS, 26 rue d'Ulm, F-75248-Paris Cedex 05, France
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Nishinaka T, Shinohara A, Ito Y, Yokoyama S, Shibata T. Base pair switching by interconversion of sugar puckers in DNA extended by proteins of RecA-family: a model for homology search in homologous genetic recombination. Proc Natl Acad Sci U S A 1998; 95:11071-6. [PMID: 9736691 PMCID: PMC21597 DOI: 10.1073/pnas.95.19.11071] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Escherichia coli RecA is a representative of proteins from the RecA family, which promote homologous pairing and strand exchange between double-stranded DNA and single-stranded DNA. These reactions are essential for homologous genetic recombination in various organisms. From NMR studies, we previously reported a novel deoxyribose-base stacking interaction between adjacent residues on the extended single-stranded DNA bound to RecA protein. In this study, we found that the same DNA structure was induced by the binding to Saccharomyces cerevisiae Rad51 protein, indicating that the unique DNA structure induced by the binding to RecA-homologs was conserved from prokaryotes to eukaryotes. On the basis of this structure, we have formulated the structure of duplex DNA within filaments formed by RecA protein and its homologs. Two types of molecular structures are presented. One is the duplex structure that has the N-type sugar pucker. Its helical pitch is approximately 95 A (18.6 bp/turn), corresponding to that of an active, or ATP-form of the RecA filament. The other is one that has the S-type sugar pucker. Its helical pitch is approximately 64 A (12.5 bp/turn), corresponding to that of an inactive, or ADP-form of the RecA filament. During this modeling, we found that the interconversion of sugar puckers between the N-type and the S-type rotates bases horizontally, while maintaining the deoxyribose-base stacking interaction. We propose that this base rotation enables base pair switching between double-stranded DNA and single-stranded DNA to take place, facilitating homologous pairing and strand exchange. A possible mechanism for strand exchange involving DNA rotation also is discussed.
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Affiliation(s)
- T Nishinaka
- Cellular and Molecular Biology Laboratory, The Institute of Physical and Chemical Research (RIKEN), Saitama 351-0198, Japan
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Araneda S, Angulo J, Touret M, Sallanon-Moulin M, Souchier C, Jouvet M. Preferential expression of kin, a nuclear protein binding to curved DNA, in the neurons of the adult rat. Brain Res 1997; 762:103-13. [PMID: 9262164 DOI: 10.1016/s0006-8993(97)00373-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The KIN17 gene product has been identified by cross immunoreactivity with anti-RecA antibodies and by DNA recombination techniques, and is probably part of the DNA recombination-repair machinery. Following Western blotting and immunocytochemistry using anti-RecA antibodies, and in situ hybridization with specific KIN17 cDNA probes, we here report the detection of high levels of KIN protein and KIN17 mRNA in the CNS of adult rats. The RecA cross-reacting protein has an apparent molecular weight of 41 kDa and is located in the nucleus of brain cells. Both the KIN17 transcript and the protein were found to be widespread, but they were present in different proportions, depending on the type of brain cells. High levels of KIN protein were seen in neurons of the motor nuclei of the brainstem, the locus coeruleus, hippocampal formation, entorhinal cortex, Purkinje cells, pyramidal cells of the cortex and mitral cells. In contrast, using a combination of KIN17 mRNA in situ hybridization and GFAP immunocytochemistry (a marker of glial cells) showed that the KIN17 messenger is preferentially transcribed in neurons, the post-mitotic and long lived brain cells. We postulate that KIN17 play a role in the illegitimate recombination of DNA sequences and/or the repair of alterations of the genome in neurons.
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Affiliation(s)
- S Araneda
- Département de Médecine Expérimentale, Faculté de Médecine, Université Claude Bernard, INSERM U52, CNRS ERS 5645, Lyon, France
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21
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Kuzminov A, Stahl FW. Stability of linear DNA in recA mutant Escherichia coli cells reflects ongoing chromosomal DNA degradation. J Bacteriol 1997; 179:880-8. [PMID: 9006046 PMCID: PMC178773 DOI: 10.1128/jb.179.3.880-888.1997] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
To study the fate of linear DNA in Escherichia coli cells, we linearized plasmid DNA at a specific site in vivo and monitored its behavior in recA mutant cells deficient in recombinational repair. Earlier, we had found that in wild-type (WT) cells linearized DNA is degraded to completion by RecBCD nuclease. We had also found that in WT cells chi sites on linear DNA inhibit RecBCD degradation by turning off its nucleolytic activities. Now we report that chi sites do not work in the absence of the RecA protein, suggesting that RecA is required in vivo to turn off the degradative activities of the RecBCD enzyme. We also report that the degradation of linearized plasmid DNA, even devoid of chi sites, is never complete in recA cells. Investigation of this linear DNA stability indicates that a fraction of recA cells are recBC phenocopies due to ongoing chromosomal DNA degradation, which titrates RecBCD nuclease. A possible role for RecBCD-promoted DNA degradation in controlling chromosomal DNA replication in E. coli is discussed.
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Affiliation(s)
- A Kuzminov
- Institute of Molecular Biology, University of Oregon, Eugene 97403, USA.
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22
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West SC. Formation, translocation and resolution of Holliday junctions during homologous genetic recombination. Philos Trans R Soc Lond B Biol Sci 1995; 347:21-5. [PMID: 7746849 DOI: 10.1098/rstb.1995.0004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Over the past three or four years, great strides have been made in our understanding of the proteins involved in recombination and the mechanisms by which recombinant molecules are formed. This review summarizes our current understanding of the process by focusing on recent studies of proteins involved in the later steps of recombination in bacteria. In particular, biochemical investigation of the in vitro properties of the E. coli RuvA, RuvB and RuvC proteins have provided our first insight into the novel insight into the novel molecular mechanisms by which Holliday junctions are moved along DNA and then resolved by endonucleolytic cleavage.
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Affiliation(s)
- S C West
- Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Herts, U.K
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Kowalczykowski SC, Dixon DA, Eggleston AK, Lauder SD, Rehrauer WM. Biochemistry of homologous recombination in Escherichia coli. Microbiol Rev 1994; 58:401-65. [PMID: 7968921 PMCID: PMC372975 DOI: 10.1128/mr.58.3.401-465.1994] [Citation(s) in RCA: 778] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Homologous recombination is a fundamental biological process. Biochemical understanding of this process is most advanced for Escherichia coli. At least 25 gene products are involved in promoting genetic exchange. At present, this includes the RecA, RecBCD (exonuclease V), RecE (exonuclease VIII), RecF, RecG, RecJ, RecN, RecOR, RecQ, RecT, RuvAB, RuvC, SbcCD, and SSB proteins, as well as DNA polymerase I, DNA gyrase, DNA topoisomerase I, DNA ligase, and DNA helicases. The activities displayed by these enzymes include homologous DNA pairing and strand exchange, helicase, branch migration, Holliday junction binding and cleavage, nuclease, ATPase, topoisomerase, DNA binding, ATP binding, polymerase, and ligase, and, collectively, they define biochemical events that are essential for efficient recombination. In addition to these needed proteins, a cis-acting recombination hot spot known as Chi (chi: 5'-GCTGGTGG-3') plays a crucial regulatory function. The biochemical steps that comprise homologous recombination can be formally divided into four parts: (i) processing of DNA molecules into suitable recombination substrates, (ii) homologous pairing of the DNA partners and the exchange of DNA strands, (iii) extension of the nascent DNA heteroduplex; and (iv) resolution of the resulting crossover structure. This review focuses on the biochemical mechanisms underlying these steps, with particular emphases on the activities of the proteins involved and on the integration of these activities into likely biochemical pathways for recombination.
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Affiliation(s)
- S C Kowalczykowski
- Division of Biological Sciences, University of California, Davis 95616-8665
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24
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Johnson A, Kolodner R. The activity of the Saccharomyces cerevisiae strand exchange protein 1 intrinsic exonuclease during joint molecule formation. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41912-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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25
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Dunderdale H, Sharples G, Lloyd R, West S. Cloning, overexpression, purification, and characterization of the Escherichia coli RuvC Holliday junction resolvase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37673-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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26
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Abstract
The crystal structure of the recA protein from Escherichia coli at 2.3-A resolution reveals a major domain that binds ADP and probably single- and double-stranded DNA. Two smaller subdomains at the N and C termini protrude from the protein and respectively stabilize a 6(1) helical polymer of protein subunits and interpolymer bundles. This polymer structure closely resembles that of recA/DNA filaments determined by electron microscopy. Mutations in recA protein that enhance coprotease, DNA-binding and/or strand-exchange activity can be explained if the interpolymer interactions in the crystal reflect a regulatory mechanism in vivo.
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Affiliation(s)
- R M Story
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511
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27
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Gruss A, Moretto V, Ehrlich SD, Duwat P, Dabert P. GC-rich DNA sequences block homologous recombination in vitro. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(20)89547-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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28
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Chiu SK, Wong BC, Chow SA. Homologous pairing in duplex DNA regions and the formation of four-stranded paranemic joints promoted by RecA protein. Effects of gap length and negative superhelicity. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)45355-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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29
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Muniyappa K, Williams K, Chase JW, Radding CM. Active nucleoprotein filaments of single-stranded binding protein and recA protein on single-stranded DNA have a regular repeating structure. Nucleic Acids Res 1990; 18:3967-73. [PMID: 2374716 PMCID: PMC331100 DOI: 10.1093/nar/18.13.3967] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
When E. coli single-stranded DNA binding protein (SSB) coats single-stranded DNA (ssDNA) in the presence of 1 mM MgCl2 it inhibits the subsequent binding of recA protein, whereas SSB binding to ssDNA in 12 mM MgCl2 promotes the binding of recA protein. These two conditions correspond respectively to those which produce 'smooth' and 'beaded' forms of ssDNA-SSB filaments. By gel filtration and immunoprecipitation we observed active nucleoprotein filaments of recA protein and SSB on ssDNA that contained on average 1 monomer of recA protein per 4 nucleotides and 1 monomer of SSB per 20-22 nucleotides. Filaments in such a mixture, when digested with micrococcal nuclease produced a regular repeating pattern, approximately every 70-80 nucleotides, that differed from the pattern observed when only recA protein was bound to the ssDNA. We conclude that the beaded ssDNA-SSB nucleoprotein filament readily binds recA protein and forms an intermediate that is active in the formation of joint molecules and can retain substantially all of the SSB that was originally bound.
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Affiliation(s)
- K Muniyappa
- Department of Human Genetics, Yale University School of Medicine, New Haven, CT 06510
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30
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Lindsley JE, Cox MM. On RecA protein-mediated homologous alignment of two DNA molecules. Three strands versus four strands. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)38794-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Conley EC, West SC. Underwinding of DNA associated with duplex-duplex pairing by RecA protein. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)38793-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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32
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Kojima M, Suzuki M, Morita T, Ogawa T, Ogawa H, Tada M. Interaction of RecA protein with pBR322 DNA modified by N-hydroxy-2-acetylaminofluorene and 4-hydroxyaminoquinoline 1-oxide. Nucleic Acids Res 1990; 18:2707-14. [PMID: 2140154 PMCID: PMC330755 DOI: 10.1093/nar/18.9.2707] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Interaction of RecA protein of Escherichia coli with pBR322 DNA modified by N-hydroxy-2-acetylaminofluorene (N-OH-AAF) and 4-hydroxyaminoquinoline 1-oxide (4HAQO) was investigated. RecA protein bound more efficiently to modified DNA than to unmodified DNA as judged by filter-binding and gel electrophoresis assay. The binding of RecA protein with modified DNA resulted in the stimulation of ATPase activity and the activation for RecA protein to stimulate the repressor cleavage. These abilities of RecA protein were increased proportionally to the number of adducts in the plasmid DNA (0-5 adducts). Apurinic and alkylated DNA did not activate RecA protein. We suggest that modification of DNA by N-OH-AAF and 4HAQO provides binding sites for RecA protein and may act as an activation signal for SOS response.
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Affiliation(s)
- M Kojima
- Laboratory of Biochemistry, Aichi Cancer Center Research Institute, Nagoya, Japan
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33
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Akaboshi E, Howard-Flanders P. RecA-ssDNA interaction: induced strand cleavage by hydroxyl radical at a defined distance from the 5' end. MOLECULAR & GENERAL GENETICS : MGG 1990; 220:456-60. [PMID: 2160054 DOI: 10.1007/bf00391753] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Interaction of the RecA protein with single-stranded DNA (ssDNA) was analyzed by challenge with the hydroxyl radical, which can cleave the DNA backbone. We found that RecA protein induces cleavage by the radical at a defined distance from the 5' end. The cleavage was at the 11th nucleotide in many oligodeoxynucleotides. Cleavage may be intermittent since a second cleavage was induced at the 22nd or 21st site. This specific cleavage was observed under optimal conditions for filament formation, homologous pairing and strand exchange. Specificity in cleavage was, however, decreased by replacement of ATP by adenosine 5'-(gamma-thio)triphosphate (ATP gamma S), replacement of RecA protein by a mutant (RecA1) protein, or an increase in Mg2+ concentration. We propose that RecA protein induces a special structural alteration, such as bending, perhaps sequentially, on ssDNA and that this altered site plays an important role in homologous pairing and strand exchange.
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Affiliation(s)
- E Akaboshi
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511
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34
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Affiliation(s)
- A I Roca
- Department of Biochemistry, University of Wisconsin-Madison 53706
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35
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DiCapua E, Schnarr M, Timmins PA. The location of DNA in complexes of recA protein with double-stranded DNA. A neutron scattering study. Biochemistry 1989; 28:3287-92. [PMID: 2663069 DOI: 10.1021/bi00434a025] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Purified recA protein is found as rodlike homopolymers, and it forms filamentous complexes with double-stranded DNA that are stable in the presence of ATP gamma S, a nonhydrolyzable analogue of ATP. The structure of these filaments has been described in some detail by electron microscopy. Here we confirm the mass per length of 6.5 recA/100 A in solution by small-angle neutron scattering and extend the analysis to homopolymers of recA protein, finding a mass per length of about 7 recA/100 A and a radial mass distribution (cross-sectional radius of gyration) significantly different for the two filaments. The models proposed so far for the structure of the complex have placed the DNA in the center of the filament. Here we verify this assumption using small-angle neutron scattering to locate the DNA in the complexes, exploiting the contrast variation method in D2O/H2O mixtures. Model calculations show that the natural contrast difference between DNA and protein is not sufficient to locate the DNA (which accounts for only 4.7% of the mass in the complex). When deuterated DNA is used, the contrast difference is enhanced, and model calculations and experiment then converge, indicating that the DNA is indeed near the axis of the complex.
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Affiliation(s)
- E DiCapua
- Institut Laue-Langevin, Grenoble, France
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36
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Freitag N, McEntee K. Affinity chromatography of RecA protein and RecA nucleoprotein complexes on RecA protein-agarose columns. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)77667-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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37
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Construction of a recombinase-deficient mutant recA protein that retains single-stranded DNA-dependent ATPase activity. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68364-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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38
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RecA-mediated strand exchange reactions between duplex DNA molecules containing damaged bases, deletions, and insertions. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68660-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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39
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Shaner SL, Radding CM. Translocation of Escherichia coli recA protein from a single-stranded tail to contiguous duplex DNA. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)48069-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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40
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Takahashi M, Kubista M, Nordén B. Linear dichroism study of RecA-DNA complexes. Structural evidence and binding stoichiometries. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47535-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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41
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Owttrim GW, Coleman JR. Molecular cloning of a recA-like gene from the cyanobacterium Anabaena variabilis. J Bacteriol 1987; 169:1824-9. [PMID: 3032896 PMCID: PMC212031 DOI: 10.1128/jb.169.5.1824-1829.1987] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A recA-like gene isolated from the cyanobacterium Anabaena variabilis was cloned and partially characterized. When introduced into Escherichia coli recA mutants, the 7.5-kilobase-pair plasmid-borne DNA insert restored resistance to methyl methanesulfonate and UV irradiation, as well as recombination proficiency when measured by Hfr-mediated conjugation. The cyanobacterial recA gene restored spontaneous but not mitomycin C-induced prophage production. Restriction analysis and subcloning yielded a 1.5-kilobase-pair Sau3A fragment which also restored methylmethane sulfonate resistance and coded for a 38- to 40-kilodalton polypeptide when expressed in an in vitro transcription-translation system.
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42
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Kokjohn TA, Miller RV. Characterization of the Pseudomonas aeruginosa recA analog and its protein product: rec-102 is a mutant allele of the P. aeruginosa PAO recA gene. J Bacteriol 1987; 169:1499-508. [PMID: 3031014 PMCID: PMC211975 DOI: 10.1128/jb.169.4.1499-1508.1987] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We cloned a 2.3-kilobase-pair fragment of the Pseudomonas aeruginosa PAO chromosome which is capable of complementing recA mutations of Escherichia coli. The recA-complementing activity was further localized to a 1.5-kilobase-pair PvuII-HindIII fragment. Southern blot analysis under conditions of high stringency indicated that DNA sequence homology is shared by the E. coli recA gene and the P. aeruginosa recA analog. The cloned recA analog was shown to restore resistance to methyl methanesulfonate, nitrofurantoin, and UV irradiation to E. coli recA mutants. Upon introduction of the cloned P. aeruginosa gene, these mutants regained recombination proficiency in HfrH-mediated conjugation and the ability to induce lambda prophages and SOS functions (din gene transcription) after exposure to DNA-damaging agents. Lambda prophage carrying a cI ind mutation was not inducible, suggesting that the mechanism of induction of these SOS functions by the P. aeruginosa RecA analog is similar to that by the activated E. coli RecA protein. The product of the recA analog was identified in minicells as a protein of approximately 47,000 daltons. Western blot analysis using anti-E. coli RecA antibody demonstrated that this protein is antigenically cross-reactive with the E. coli recA protein. The recA-containing fragment was cloned into the broad-host-range vector pCP13 and introduced into Rec- strains of P. aeruginosa containing the rec-102 allele. The plasmid was shown to restore recombination proficiency in FP5-mediated conjugations and to restore resistance to UV irradiation and methyl methanesulfonate to these Rec- mutants. It was shown that a wild-type allele of rec-102 is necessary for UV-mediated induction of D3 and F116 prophages. The cloned recA analog restored the UV inducibility of these prophages in rec-102 mutants. These data indicate that rec-102 is a mutant allele of the P. aeruginosa recA gene and suggest that there has been considerable conservation of the recA gene in the evolution of the gram-negative bacteria.
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43
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ATP-independent renaturation of complementary DNA strands by the mutant recA1 protein from Escherichia coli. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)69259-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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44
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Neuendorf SK, Cox MM. Exchange of recA protein between adjacent recA protein-single-stranded DNA complexes. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)83907-8] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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45
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46
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Cassuto E, Howard-Flanders P. The binding of RecA protein to duplex DNA molecules is directional and is promoted by a single stranded region. Nucleic Acids Res 1986; 14:1149-57. [PMID: 3513121 PMCID: PMC339494 DOI: 10.1093/nar/14.3.1149] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
RecA protein from E. coli binds more strongly to single stranded DNA than to duplex molecules. Using duplex DNA that contains single stranded gaps, we have studied the protection by RecA protein at various concentrations, of restriction sites as a function of their distance from the single stranded region. We show that the binding of RecA protein, initiated in the single stranded region, extends progressively along the adjoining duplex in the 5' to 3' direction with respect to the single stranded region. The strand exchange reaction is known to proceed in the same direction.
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47
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Abbott PJ. Stimulation of recombination between homologous sequences on carcinogen-treated plasmid DNA and chromosomal DNA by induction of the SOS response in Escherichia coli K12. MOLECULAR & GENERAL GENETICS : MGG 1985; 201:129-32. [PMID: 3932820 DOI: 10.1007/bf00397998] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Previous studies have shown that transformation of Escherichia coli by plasmid DNA modified in vitro by carcinogens leads to RecA-dependant recombination between homologous plasmid and chromosomal DNA sequences. The mechanism of this recombination has now been studied using recombination-deficient mutants, and the influence of induction of the SOS response on the level of recombination investigated. Plasmid pNO1523, containing the str+ operon (Sms), has been modified in vitro by either irradiation with UV light, or by reaction with (+/-) trans-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) and used to transform streptomycin-resistant hosts. The formation of Ampr transformants which also carry streptomycin resistance was used as a measure of the level of recombination between plasmid and chromosomal DNA. Transformation of recB and recC mutants produced no change in the level of recombination while in the recF mutant a significant decrease was observed compared to the wild type host. Thermal induction of the SOS response in tif-1 and tif-1 umuC mutants followed by transformation led to a four-fold increase in recombination in both cases. The results suggest that the streptomycin-resistant transformants arise exclusively via a recombinational pathway which is largely dependant on the recF gene product, and that this pathway is influenced by induction of the SOS response. These results are discussed in terms of the mechanism of this recombination.
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Abstract
The recA gene of Pseudomonas aeruginosa PAO has been isolated and introduced into Escherichia coli K-12. Resistance to killing by UV irradiation was restored in several RecA-E. coli K-12 hosts by the P. aeruginosa gene, as was resistance to methyl methanesulfonate. Recombination proficiency was also restored, as measured by HfrH-mediated conjugation and by the ability to propagate Fec-phage lambda derivatives. The cloned P. aeruginosa recA gene restored both spontaneous and mitomycin C-stimulated induction of lambda prophage in lysogens of a recA strain of E. coli K-12.
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49
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10 nm RecA protein filaments formed in the presence of Mg2+ and ATP gamma S may contain RNA. MOLECULAR & GENERAL GENETICS : MGG 1985; 199:415-20. [PMID: 2412090 DOI: 10.1007/bf00330752] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Filaments formed by the polymerization of RecA protein along DNA in the presence of Mg2+ and adenosine 5'-0-(3-thiotriphosphate) (ATP gamma S) are seen by electron microscopy to have a 10 nm diameter with a 9 nm helical repeat. When certain preparations of apparently pure RecA protein are incubated with Mg2+ and ATP gamma S in the absence of nucleic acid for extended times, very long filaments with the same 10 nm diameter and 9 nm axial repeat are seen. We show here that these long 10 nm filaments can contain RNA which is present as a contaminant of the RecA protein and poly(A) which is synthesized during the incubations by an activity that is apparently polynucleotide phosphorylase. RecA protein purified by a procedure developed in this laboratory did not contain RNA and did not form these very long 10 nm filaments. However, when exogenous RNA was added to this protein, 10 nm filament formation was observed.
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50
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