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Balouchi M, Huang SH, McGrath SL, Kobryn K. The telomere resolvase, TelA, utilizes an underwound pre-cleavage intermediate to promote hairpin telomere formation. PLoS One 2023; 18:e0294732. [PMID: 38019799 PMCID: PMC10686437 DOI: 10.1371/journal.pone.0294732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 11/06/2023] [Indexed: 12/01/2023] Open
Abstract
The telomere resolvase, TelA, forms the hairpin telomeres of the linear chromosome of Agrobacterium tumefaciens in a process referred to as telomere resolution. Telomere resolution is a unique DNA cleavage and rejoining reaction that resolves replicated telomere junctions into a pair of hairpin telomeres. Telomere resolvases utilize a reaction mechanism with similarities to that of topoisomerase-IB enzymes and tyrosine recombinases. The reaction proceeds without the need for high-energy cofactors due to the use of a covalent, enzyme-cleaved DNA intermediate that stores the bond energy of the cleaved bonds in 3'-phosphotyrosyl linkages. The cleaved DNA strands are then refolded into a hairpin conformation and the 5'-OH ends of the refolded strands attack the 3'-phosphotyrosine linkages in order to rejoin the DNA strands into hairpin telomeres. Because this kind of reaction mechanism is, in principle, reversible it is unclear how TelA controls the direction of the reaction and propels the reaction to completion. We present evidence that TelA forms and/or stabilizes a pre-cleavage intermediate that features breakage of the four central basepairs between the scissile phosphates prior to DNA cleavage to help propel the reaction forwards, thus preventing abortive cleavage and rejoining cycles that regenerate the substrate DNA. We identify eight TelA sidechains, located in the hairpin-binding module and catalytic domains of TelA, implicated in this process. These mutants were deficient for telomere resolution on parental replicated telomere junctions but were rescued by introduction of substrate modifications that mimic unwinding of the DNA between the scissile phosphates.
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Affiliation(s)
- Mahrokh Balouchi
- Dept. of Biochemistry, Microbiology & Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Shu Hui Huang
- Dept. of Biochemistry, Microbiology & Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Siobhan L. McGrath
- The Global Institute for Food Security, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Kerri Kobryn
- Dept. of Biochemistry, Microbiology & Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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McGrath SL, Huang SH, Kobryn K. The N-terminal domain of the Agrobacterium tumefaciens telomere resolvase, TelA, regulates its DNA cleavage and rejoining activities. J Biol Chem 2022; 298:101951. [PMID: 35447111 PMCID: PMC9111995 DOI: 10.1016/j.jbc.2022.101951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 04/08/2022] [Accepted: 04/09/2022] [Indexed: 12/04/2022] Open
Abstract
Linear replicons can be found in a minority of prokaryotic organisms, including Borrelia species and Agrobacterium tumefaciens. The problem with replicating the lagging strand end of linear DNAs is circumvented in these organisms by the presence of covalently closed DNA hairpin telomeres at the DNA termini. Telomere resolvases are enzymes responsible for generating these hairpin telomeres from a dimeric replication intermediate through a two-step DNA cleavage and rejoining reaction referred to as telomere resolution. It was previously shown that the agrobacterial telomere resolvase, TelA, possesses ssDNA annealing activity in addition to telomere resolution activity. The annealing activity derives, chiefly, from the N-terminal domain. This domain is dispensable for telomere resolution. In this study, we used activity analyses of an N-terminal domain deletion mutant, domain add back experiments, and protein–protein interaction studies and we report that the N-terminal domain of TelA is involved in inhibitory interactions with the remainder of TelA that are relieved by the binding of divalent metal ions. We also found that the regulation of telomere resolution by the N-terminal domain of TelA extends to suppression of inappropriate enzymatic activity, including hairpin telomere fusion (reaction reversal) and recombination between replicated telomeres to form a Holliday junction.
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Affiliation(s)
- Siobhan L McGrath
- Department of Biochemistry, Microbiology & Immunology, College of Medicine, University of Saskatchewan, Academic Health Sciences Building, Saskatoon, Saskatchewan, Canada
| | - Shu Hui Huang
- Department of Biochemistry, Microbiology & Immunology, College of Medicine, University of Saskatchewan, Academic Health Sciences Building, Saskatoon, Saskatchewan, Canada
| | - Kerri Kobryn
- Department of Biochemistry, Microbiology & Immunology, College of Medicine, University of Saskatchewan, Academic Health Sciences Building, Saskatoon, Saskatchewan, Canada.
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Taylor JA, Seol Y, Budhathoki J, Neuman KC, Mizuuchi K. CTP and parS coordinate ParB partition complex dynamics and ParA-ATPase activation for ParABS-mediated DNA partitioning. eLife 2021; 10:65651. [PMID: 34286695 PMCID: PMC8357417 DOI: 10.7554/elife.65651] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 07/20/2021] [Indexed: 11/13/2022] Open
Abstract
ParABS partition systems, comprising the centromere-like DNA sequence parS, the parS-binding ParB-CTPase, and the nucleoid-binding ParA-ATPase, ensure faithful segregation of bacterial chromosomes and low-copy-number plasmids. F-plasmid partition complexes containing ParBF and parSF move by generating and following a local concentration gradient of nucleoid-bound ParAF. However, the process through which ParBF activates ParAF-ATPase has not been defined. We studied CTP- and parSF-modulated ParAF-ParBF complex assembly, in which DNA-bound ParAF-ATP dimers are activated for ATP hydrolysis by interacting with two ParBF N-terminal domains. CTP or parSF enhances the ATPase rate without significantly accelerating ParAF-ParBF complex assembly. Together, parSF and CTP accelerate ParAF-ParBF assembly without further significant increase in ATPase rate. Magnetic-tweezers experiments showed that CTP promotes multiple ParBF loading onto parSF-containing DNA, generating condensed partition complex-like assemblies. We propose that ParBF in the partition complex adopts a conformation that enhances ParBF-ParBF and ParAF-ParBF interactions promoting efficient partitioning.
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Affiliation(s)
- James A Taylor
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Yeonee Seol
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Jagat Budhathoki
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Keir C Neuman
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Kiyoshi Mizuuchi
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
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Taylor JA, Seol Y, Budhathoki J, Neuman KC, Mizuuchi K. CTP and parS coordinate ParB partition complex dynamics and ParA-ATPase activation for ParABS-mediated DNA partitioning. eLife 2021; 10:65651. [PMID: 34286695 DOI: 10.1101/2021.01.24.427996] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 07/20/2021] [Indexed: 05/25/2023] Open
Abstract
ParABS partition systems, comprising the centromere-like DNA sequence parS, the parS-binding ParB-CTPase, and the nucleoid-binding ParA-ATPase, ensure faithful segregation of bacterial chromosomes and low-copy-number plasmids. F-plasmid partition complexes containing ParBF and parSF move by generating and following a local concentration gradient of nucleoid-bound ParAF. However, the process through which ParBF activates ParAF-ATPase has not been defined. We studied CTP- and parSF-modulated ParAF-ParBF complex assembly, in which DNA-bound ParAF-ATP dimers are activated for ATP hydrolysis by interacting with two ParBF N-terminal domains. CTP or parSF enhances the ATPase rate without significantly accelerating ParAF-ParBF complex assembly. Together, parSF and CTP accelerate ParAF-ParBF assembly without further significant increase in ATPase rate. Magnetic-tweezers experiments showed that CTP promotes multiple ParBF loading onto parSF-containing DNA, generating condensed partition complex-like assemblies. We propose that ParBF in the partition complex adopts a conformation that enhances ParBF-ParBF and ParAF-ParBF interactions promoting efficient partitioning.
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Affiliation(s)
- James A Taylor
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Yeonee Seol
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Jagat Budhathoki
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Keir C Neuman
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Kiyoshi Mizuuchi
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
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McGrath SL, Huang SH, Kobryn K. Single stranded DNA annealing is a conserved activity of telomere resolvases. PLoS One 2021; 16:e0246212. [PMID: 33539370 PMCID: PMC7861564 DOI: 10.1371/journal.pone.0246212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 01/14/2021] [Indexed: 12/26/2022] Open
Abstract
Bacterial species of the genera Agrobacterium and Borrelia possess chromosomes terminated by hairpin telomeres. Replication produces dimeric replication intermediates fused via replicated telomere junctions. A specialized class of enzymes, referred to as telomere resolvases, promotes the resolution of the replicated intermediate into linear monomers terminated by hairpin telomeres. Telomere resolution is catalyzed via DNA cleavage and rejoining events mechanistically similar to those promoted by topoisomerase-IB and tyrosine recombinase enzymes. Examination of the borrelial telomere resolvase, ResT, revealed unanticipated multifunctionality; aside from its expected telomere resolution activity ResT possessed a singled-stranded DNA (ssDNA) annealing activity that extended to both naked ssDNA and ssDNA complexed with its cognate single-stranded DNA binding protein (SSB). At present, the role this DNA annealing activity plays in vivo remains unknown. We have demonstrated here that single-stranded DNA annealing is also a conserved property of the agrobacterial telomere resolvase, TelA. This activity in TelA similarly extends to both naked ssDNA and ssDNA bound by its cognate SSB. TelA's annealing activity was shown to stem from the N-terminal domain; removal of this domain abolished annealing without affecting telomere resolution. Further, independent expression of the N-terminal domain of TelA produced a functional annealing protein. We suggest that the apparent conservation of annealing activity in two telomere resolvases, from distantly related bacterial species, implies a role for this activity in hairpin telomere metabolism. Our demonstration of the separation of the telomere resolution and annealing activities of TelA provides a platform for future experiments aimed at identifying the role DNA annealing performs in vivo.
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Affiliation(s)
- Siobhan L. McGrath
- Department of Microbiology & Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Shu Hui Huang
- Department of Microbiology & Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Kerri Kobryn
- Department of Microbiology & Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- * E-mail:
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Abstract
TelN and tos are a unique DNA linearization unit isolated from bacteriophage N15. While being transferable, the TelN cleaving-rejoining activities remained stable to function on tos in both bacterial and mammalian environments. However, TelN contribution in linear plasmid replication in mammalian cells remains unknown. Herein, we investigated the association of TelN in linear tos-containing DNA (tos-DNA) replication in mammalian cells. Additionally, the mammalian origin of replication (ori) that is well-known to initiate the replication event of plasmid vectors was also studied. In doing so, we identified that both TelN and mammalian initiation sites were essential for the replication of linear tos-DNA, determined by using methylation sensitive DpnI/MboI digestion and polymerase chain reaction (PCR) amplification approaches. Furthermore, we engineered the linear tos-DNA to be able to retain in mammalian cells using S/MAR technology. The resulting S/MAR containing tos-DNA was robust for at least 15 days, with (1) continuous tos-DNA replication, (2) correct splicing of gene transcripts, and (3) stable exogenous gene expression that was statistically comparable to the endogenous gene expression level. Understanding the activities of TelN and tos in mammalian cells can potentially provide insights for adapting this simple DNA linearization unit in developing novel genetic engineering tools, especially to the eukaryotic telomere/telomerase study.
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Affiliation(s)
- Pei Sheng Liew
- School of Science, Monash University Malaysia, Bandar Sunway, 47500 Selangor Darul Ehsan, Malaysia
| | - Tze Hao Tan
- Faculty of Science, Kyushu University, Ito campus, Fukuoka 819-0395, Japan
| | - Yin Cheng Wong
- School of Science, Monash University Malaysia, Bandar Sunway, 47500 Selangor Darul Ehsan, Malaysia
| | - Edmund Ui Hang Sim
- Faculty of Resource Sciences and Technology, University Malaysia Sarawak, 94300 Kota Samarahan, Malaysia
| | - Choon Weng Lee
- Institute of Biological Science, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Kumaran Narayanan
- School of Science, Monash University Malaysia, Bandar Sunway, 47500 Selangor Darul Ehsan, Malaysia
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Liew PS, Chen Q, Ng AWR, Chew YC, Ravin NV, Sim EUH, Lee CW, Narayanan K. Phage N15 protelomerase resolves its tos recognition site into hairpin telomeres within mammalian cells. Anal Biochem 2019; 583:113361. [DOI: 10.1016/j.ab.2019.113361] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 07/09/2019] [Accepted: 07/09/2019] [Indexed: 11/30/2022]
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Huang SH, Cozart MR, Hart MA, Kobryn K. The Borrelia burgdorferi telomere resolvase, ResT, possesses ATP-dependent DNA unwinding activity. Nucleic Acids Res 2017; 45:1319-1329. [PMID: 28180323 PMCID: PMC5388405 DOI: 10.1093/nar/gkw1243] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 11/23/2016] [Accepted: 11/28/2016] [Indexed: 11/14/2022] Open
Abstract
Spirochetes of the genus Borrelia possess unusual genomes harboring multiple linear and circular replicons. The linear replicons are terminated by covalently closed hairpin (hp) telomeres. Hairpin telomeres are formed from replicated intermediates by the telomere resolvase, ResT, in a phosphoryl transfer reaction with mechanistic similarities to those promoted by type 1B topoisomerases and tyrosine recombinases. There is growing evidence that ResT is multifunctional. Upon ResT depletion DNA replication unexpectedly ceases. Additionally, ResT possesses RecO-like biochemical activities being able to promote single-strand annealing on both free ssDNA and ssDNA complexed with cognate single-stranded DNA binding protein. We report here that ResT possesses DNA-dependent ATPase activity that promotes DNA unwinding with a 3΄-5΄ polarity. ResT can unwind a variety of substrates including synthetic replication forks and D-loops. We demonstrate that ResT's twin activities of DNA unwinding and annealing can drive regression of a model replication fork. These properties are similar to those of the RecQ helicase of the RecF pathway involved in DNA gap repair. We propose that ResT's combination of activities implicates it in replication and recombination processes operating on the linear chromosome and plasmids of Borrelia burgdorferi.
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Affiliation(s)
- Shu Hui Huang
- Department of Microbiology & Immunology, College of Medicine, University of Saskatchewan Academic Health Sciences Building, 107 Wiggins Rd, Saskatoon, SK, Canada
| | - McKayla R Cozart
- Department of Microbiology & Immunology, College of Medicine, University of Saskatchewan Academic Health Sciences Building, 107 Wiggins Rd, Saskatoon, SK, Canada
| | - Madison A Hart
- Department of Microbiology & Immunology, College of Medicine, University of Saskatchewan Academic Health Sciences Building, 107 Wiggins Rd, Saskatoon, SK, Canada
| | - Kerri Kobryn
- Department of Microbiology & Immunology, College of Medicine, University of Saskatchewan Academic Health Sciences Building, 107 Wiggins Rd, Saskatoon, SK, Canada
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Karlsen C, Hjerde E, Klemetsen T, Willassen NP. Pan genome and CRISPR analyses of the bacterial fish pathogen Moritella viscosa. BMC Genomics 2017; 18:313. [PMID: 28427330 PMCID: PMC5399434 DOI: 10.1186/s12864-017-3693-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 04/06/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Winter-ulcer Moritella viscosa infections continue to be a significant burden in Atlantic salmon (Salmo salar L.) farming. M. viscosa comprises two main clusters that differ in genetic variation and phenotypes including virulence. Horizontal gene transfer through acquisition and loss of mobile genetic elements (MGEs) is a major driving force of bacterial diversification. To gain insight into genomic traits that could affect sublineage evolution within this bacterium we examined the genome sequences of twelve M. viscosa strains. Matches between M. viscosa clustered, regularly interspaced, short palindromic, repeats and associated cas genes (CRISPR-Cas) were analysed to correlate CRISPR-Cas with adaptive immunity against MGEs. RESULTS The comparative genomic analysis of M. viscosa isolates from across the North Atlantic region and from different fish species support delineation of M. viscosa into four phylogenetic lineages. The results showed that M. viscosa carries two distinct variants of the CRISPR-Cas subtype I-F systems and that CRISPR features follow the phylogenetic lineages. A subset of the spacer content match prophage and plasmid genes dispersed among the M. viscosa strains. Further analysis revealed that prophage and plasmid-like element distribution were reflected in the content of the CRISPR-spacer profiles. CONCLUSIONS Our data suggests that CRISPR-Cas mediated interactions with MGEs impact genome properties among M. viscosa, and that patterns in spacer and MGE distributions are linked to strain relationships.
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Affiliation(s)
- Christian Karlsen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences (NMBU), Pb 8146 Dep., 0033, Oslo, Norway. .,Present address: Nofima AS, Division of Aquaculture, PO Box 210, Ås, N-1431, Norway.
| | - Erik Hjerde
- Department of Chemistry, Faculty of Science and Technology, University of Tromsø, N-9037, Tromsø, Norway
| | - Terje Klemetsen
- Department of Chemistry, Faculty of Science and Technology, University of Tromsø, N-9037, Tromsø, Norway
| | - Nils Peder Willassen
- Department of Chemistry, Faculty of Science and Technology, University of Tromsø, N-9037, Tromsø, Norway.,The Norwegian Structural Biology Centre, University of Tromsø, N-9037, Tromsø, Norway
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Huang SH, Kobryn K. The Borrelia burgdorferi telomere resolvase, ResT, anneals ssDNA complexed with its cognate ssDNA-binding protein. Nucleic Acids Res 2016; 44:5288-98. [PMID: 27131360 PMCID: PMC4914115 DOI: 10.1093/nar/gkw344] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/18/2016] [Indexed: 11/12/2022] Open
Abstract
Spirochetes of the genus Borrelia possess unusual genomes that consist in a linear chromosome and multiple linear and circular plasmids. The linear replicons are terminated by covalently closed hairpin ends, referred to as hairpin telomeres. The hairpin telomeres represent a simple solution to the end-replication problem. Deoxyribonucleic acid replication initiates internally and proceeds bidirectionally toward the hairpin telomeres. The telomere resolvase, ResT, forms the hairpin telomeres from replicated telomere intermediates in a reaction with similarities to those promoted by type IB topoisomerases and tyrosine recombinases. ResT has also been shown to possess DNA single-strand annealing activity. We report here that ResT promotes single-strand annealing of both free DNA strands and ssDNA complexed with single-stranded DNA binding protein (SSB). The annealing of complementary strands bound by SSB requires a ResT-SSB interaction that is mediated by the conserved amphipathic C-terminal tail of SSB. These properties of ResT are similar to those demonstrated for the recombination mediator protein, RecO, of the RecF pathway. Borrelia burgdorferi is unusual in lacking identifiable homologs of the RecFOR proteins. We propose that ResT may provide missing RecFOR functions.
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Affiliation(s)
- Shu Hui Huang
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan Academic Health Sciences Building, 107 Wiggins Rd, Saskatoon, SK S7N 5E5, Canada
| | - Kerri Kobryn
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan Academic Health Sciences Building, 107 Wiggins Rd, Saskatoon, SK S7N 5E5, Canada
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Abstract
The lambdoid phage N15 of Escherichia coli is very unusual among temperate phages in that its prophage is not integrated into the chromosome but is a linear plasmid molecule with covalently closed ends (telomeres). Upon infection, the phage DNA circularizes via cohesive ends, and then a special phage enzyme of the tyrosine recombinase family, protelomerase, cuts at another site and joins the ends, forming hairpin telomeres of the linear plasmid prophage. Replication of the N15 prophage is initiated at an internally located ori site and proceeds bidirectionally, resulting in the formation of duplicated telomeres. The N15 protelomerase cuts them, generating two linear plasmid molecules with hairpin telomeres. Stable inheritance of the plasmid prophage is ensured by a partitioning operon similar to the F factor sop operon. Unlike the F centromere, the N15 centromere consists of four inverted repeats dispersed in the genome. The multiplicity and dispersion of centromeres are required for efficient partitioning of a linear plasmid. The centromeres are located in the N15 genome regions involved in phage replication and control of lytic development, and binding of partition proteins at these sites regulates these processes. The family of N15-like linear phage-plasmids includes lambdoid phages ɸKO2 and pY54, as well as Myoviridae phages ΦHAP-1, VHML, VP882, Vp58.5, and vB_VpaM_MAR of marine gamma-proteobacteria. The genomes of these phages contain similar protelomerase genes, lysogeny control modules, and replication genes, suggesting that these phages may belong to a group diverged from a common ancestor.
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McFarland KN, Liu J, Landrian I, Godiska R, Shanker S, Yu F, Farmerie WG, Ashizawa T. SMRT Sequencing of Long Tandem Nucleotide Repeats in SCA10 Reveals Unique Insight of Repeat Expansion Structure. PLoS One 2015; 10:e0135906. [PMID: 26295943 PMCID: PMC4546671 DOI: 10.1371/journal.pone.0135906] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 07/28/2015] [Indexed: 12/02/2022] Open
Abstract
A large, non-coding ATTCT repeat expansion causes the neurodegenerative disorder, spinocerebellar ataxia type 10 (SCA10). In a subset of SCA10 patients, interruption motifs are present at the 5’ end of the expansion and strongly correlate with epileptic seizures. Thus, interruption motifs are a predictor of the epileptic phenotype and are hypothesized to act as a phenotypic modifier in SCA10. Yet, the exact internal sequence structure of SCA10 expansions remains unknown due to limitations in current technologies for sequencing across long extended tracts of tandem nucleotide repeats. We used the third generation sequencing technology, Single Molecule Real Time (SMRT) sequencing, to obtain full-length contiguous expansion sequences, ranging from 2.5 to 4.4 kb in length, from three SCA10 patients with different clinical presentations. We obtained sequence spanning the entire length of the expansion and identified the structure of known and novel interruption motifs within the SCA10 expansion. The exact interruption patterns in expanded SCA10 alleles will allow us to further investigate the potential contributions of these interrupting sequences to the pathogenic modification leading to the epilepsy phenotype in SCA10. Our results also demonstrate that SMRT sequencing is useful for deciphering long tandem repeats that pose as “gaps” in the human genome sequence.
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Affiliation(s)
- Karen N. McFarland
- Department of Neurology and The McKnight Brain Institute, University of Florida, Gainesville, Florida, 32610, United States of America
| | - Jilin Liu
- Department of Neurology and The McKnight Brain Institute, University of Florida, Gainesville, Florida, 32610, United States of America
| | - Ivette Landrian
- Department of Neurology and The McKnight Brain Institute, University of Florida, Gainesville, Florida, 32610, United States of America
| | - Ronald Godiska
- Lucigen Corporation, Middleton, Wisconsin, 53562, United States of America
| | - Savita Shanker
- Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida, 32610, United States of America
| | - Fahong Yu
- Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida, 32610, United States of America
| | - William G. Farmerie
- Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, Florida, 32610, United States of America
| | - Tetsuo Ashizawa
- Department of Neurology and The McKnight Brain Institute, University of Florida, Gainesville, Florida, 32610, United States of America
- * E-mail:
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13
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Raftis EJ, Forde BM, Claesson MJ, O'Toole PW. Unusual genome complexity in Lactobacillus salivarius JCM1046. BMC Genomics 2014; 15:771. [PMID: 25201645 PMCID: PMC4165912 DOI: 10.1186/1471-2164-15-771] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 08/26/2014] [Indexed: 12/31/2022] Open
Abstract
Background Lactobacillus salivarius strains are increasingly being exploited for their probiotic properties in humans and animals. Dissemination of antibiotic resistance genes among species with food or probiotic-association is undesirable and is often mediated by plasmids or integrative and conjugative elements. L. salivarius strains typically have multireplicon genomes including circular megaplasmids that encode strain-specific traits for intestinal survival and probiotic activity. Linear plasmids are less common in lactobacilli and show a very limited distribution in L. salivarius. Here we present experimental evidence that supports an unusually complex multireplicon genome structure in the porcine isolate L. salivarius JCM1046. Results JCM1046 harbours a 1.83 Mb chromosome, and four plasmids which constitute 20% of the genome. In addition to the known 219 kb repA-type megaplasmid pMP1046A, we identified and experimentally validated the topology of three additional replicons, the circular pMP1046B (129 kb), a linear plasmid pLMP1046 (101 kb) and pCTN1046 (33 kb) harbouring a conjugative transposon. pMP1046B harbours both plasmid-associated replication genes and paralogues of chromosomally encoded housekeeping and information-processing related genes, thus qualifying it as a putative chromid. pLMP1046 shares limited sequence homology or gene synteny with other L. salivarius plasmids, and its putative replication-associated protein is homologous to the RepA/E proteins found in the large circular megaplasmids of L. salivarius. Plasmid pCTN1046 harbours a single copy of an integrated conjugative transposon (Tn6224) which appears to be functionally intact and includes the tetracycline resistance gene tetM. Conclusion Experimental validation of sequence assemblies and plasmid topology resolved the complex genome architecture of L. salivarius JCM1046. A high-coverage draft genome sequence would not have elucidated the genome complexity in this strain. Given the expanding use of L. salivarius as a probiotic, it is important to determine the genotypic and phenotypic organization of L. salivarius strains. The identification of Tn6224-like elements in this species has implications for strain selection for probiotic applications. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-771) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | - Paul W O'Toole
- School of Microbiology University College Cork, Cork, Ireland.
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14
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Abstract
A number of attempts have been made to simplify the synthesis of whole chromosomes to generate artificial microorganisms. However, the sheer size of the average bacterial genome makes the task virtually impracticable. A major limitation is the maximum assembly DNA size imposed by the current available technologies. We propose to fragment the bacterial chromosome into autonomous replicating units so that (i) each episome becomes small enough to be assembled in its entirety within an assembly host and (ii) the complete episome set should be able to generate a viable cell. In this work, we used the telN/tos system of bacteriophage N1 to show that the circular genome of Escherichia coli can be split into two linear chromosomes that complement each other to produce viable cells.
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Affiliation(s)
- Xiquan Liang
- Life Technologies, 5791 Van Allen Way, Carlsbad, California 92008, United States
| | - Chang-Ho Baek
- Life Technologies, 5791 Van Allen Way, Carlsbad, California 92008, United States
| | - Federico Katzen
- Life Technologies, 5791 Van Allen Way, Carlsbad, California 92008, United States
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15
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Mir T, Huang SH, Kobryn K. The telomere resolvase of the Lyme disease spirochete, Borrelia burgdorferi, promotes DNA single-strand annealing and strand exchange. Nucleic Acids Res 2013; 41:10438-48. [PMID: 24049070 PMCID: PMC3905847 DOI: 10.1093/nar/gkt832] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Spirochetes of the genus Borrelia include the tick-transmitted causative agents of Lyme disease and relapsing fever. They possess unusual genomes composed mainly of linear replicons terminated by closed DNA hairpin telomeres. Hairpin telomeres present an uninterrupted DNA chain to the replication machinery overcoming the 'end-replication problem' for the linear replicons. Hairpin telomeres are formed from inverted repeat replicated telomere junctions by the telomere resolvase, ResT. ResT uses a reaction mechanism similar to that of the type IB topoisomerases and tyrosine recombinases. We report here that ResT also possesses single-strand annealing activity and a limited ability to promote DNA strand exchange reactions on partial duplex substrates. This combination of activities suggests ResT is a nexus between the seemingly distinct processes of telomere resolution and homologous recombination. Implications for hairpin telomere replication and linear plasmid recombination, including antigenic variation, are discussed.
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Affiliation(s)
- Taskia Mir
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan, Academic Health Sciences Building, 107 Wiggins Rd, Saskatoon, SK S7N 5E5, Canada
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16
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Shi K, Huang WM, Aihara H. An enzyme-catalyzed multistep DNA refolding mechanism in hairpin telomere formation. PLoS Biol 2013; 11:e1001472. [PMID: 23382649 PMCID: PMC3558466 DOI: 10.1371/journal.pbio.1001472] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 12/12/2012] [Indexed: 12/19/2022] Open
Abstract
Crystal structures reveal catalysis of DNA refolding in the molecular mechanism underlying generation of bacterial hairpin telomeres. Hairpin telomeres of bacterial linear chromosomes are generated by a DNA cutting–rejoining enzyme protelomerase. Protelomerase resolves a concatenated dimer of chromosomes as the last step of chromosome replication, converting a palindromic DNA sequence at the junctions between chromosomes into covalently closed hairpins. The mechanism by which protelomerase transforms a duplex DNA substrate into the hairpin telomeres remains largely unknown. We report here a series of crystal structures of the protelomerase TelA bound to DNA that represent distinct stages along the reaction pathway. The structures suggest that TelA converts a linear duplex substrate into hairpin turns via a transient strand-refolding intermediate that involves DNA-base flipping and wobble base-pairs. The extremely compact di-nucleotide hairpin structure of the product is fully stabilized by TelA prior to strand ligation, which drives the reaction to completion. The enzyme-catalyzed, multistep strand refolding is a novel mechanism in DNA rearrangement reactions. Linear chromosomes capped by hairpin telomeres are widespread in prokaryotes and are found in important bacterial pathogens. However, three-dimensional structure of the hairpin telomere, as well as the molecular mechanisms underlying its generation, has remained poorly understood. In this work, we investigated how the enzyme responsible for generating the bacterial hairpin telomeres (protelomerase, also known as telomere resolvase) transforms a linear double-stranded DNA molecule into sharp hairpin turns. Our X-ray crystallographic and biochemical data collectively suggest that protelomerase employs a multistep DNA strand-refolding mechanism as described below. Protelomerase first cleaves both strands of a double-helical DNA substrate and reshapes the DNA strands into a transition state conformation (refolding intermediate) stabilized by specific protein–DNA and DNA–DNA interactions including noncanonical (non-Watson–Crick) base-pairs. The DNA strands are then refolded into extremely compact hairpin products, stabilized by a set of interactions distinct from those stabilizing the refolding intermediate. We believe that an enzyme “catalyzing” not only the chemical reactions of DNA strand cutting/rejoining but also the ordered transition between different DNA conformations to guide refolding of the DNA strand is a novel concept, and we suspect that similar mechanisms may be employed by other enzymes involved in conformational changes/refolding of biological macromolecules.
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Affiliation(s)
- Ke Shi
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Wai Mun Huang
- Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, Utah, United States of America
| | - Hideki Aihara
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
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17
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Pinto UM, Pappas KM, Winans SC. The ABCs of plasmid replication and segregation. Nat Rev Microbiol 2013; 10:755-65. [PMID: 23070556 DOI: 10.1038/nrmicro2882] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
To ensure faithful transmission of low-copy plasmids to daughter cells, these plasmids must replicate once per cell cycle and distribute the replicated DNA to the nascent daughter cells. RepABC family plasmids are found exclusively in alphaproteobacteria and carry a combined replication and partitioning locus, the repABC cassette, which is also found on secondary chromosomes in this group. RepC and a replication origin are essential for plasmid replication, and RepA, RepB and the partitioning sites distribute the replicons to predivisional cells. Here, we review our current understanding of the transcriptional and post-transcriptional regulation of the Rep proteins and of their functions in plasmid replication and partitioning.
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Affiliation(s)
- Uelinton M Pinto
- Departamento de Alimentos, Universidade Federal de Ouro Preto, Morro do Cruzeiro, Ouro Preto, Minas Gerais 35400-000, Brazil
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18
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Structure-function analysis of the SaPIbov1 replication origin in Staphylococcus aureus. Plasmid 2012; 67:183-90. [PMID: 22281159 DOI: 10.1016/j.plasmid.2012.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/04/2012] [Accepted: 01/05/2012] [Indexed: 11/20/2022]
Abstract
The SaPIs and their relatives are phage satellites and are unique among the known bacterial pathogenicity islands in their ability to replicate autonomously. They possess a phage-like replicon, which is organized as two sets of iterons arrayed symmetrically to flank an AT-rich region that is driven to melt by the binding of a SaPI-specific initiator (Rep) to the flanking iterons. Extensive deletion analysis has revealed that Rep can bind to a single iteron, generating a simple shift in a gel mobility assay; when bound on both sides, a second retarded band is seen, suggesting independent binding. Binding to both sites of the ori is necessary but not sufficient to melt the AT-rich region and initiate replication. For these processes, virtually the entire origin must be present. Since SaPI replication can be initiated on linear DNA, it is suggested that bilateral binding may be necessary to constrain the intervening DNA to enable Rep-driven melting.
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19
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Jalan N, Aritua V, Kumar D, Yu F, Jones JB, Graham JH, Setubal JC, Wang N. Comparative genomic analysis of Xanthomonas axonopodis pv. citrumelo F1, which causes citrus bacterial spot disease, and related strains provides insights into virulence and host specificity. J Bacteriol 2011; 193:6342-57. [PMID: 21908674 PMCID: PMC3209208 DOI: 10.1128/jb.05777-11] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2011] [Accepted: 08/30/2011] [Indexed: 11/20/2022] Open
Abstract
Xanthomonas axonopodis pv. citrumelo is a citrus pathogen causing citrus bacterial spot disease that is geographically restricted within the state of Florida. Illumina, 454 sequencing, and optical mapping were used to obtain a complete genome sequence of X. axonopodis pv. citrumelo strain F1, 4.9 Mb in size. The strain lacks plasmids, in contrast to other citrus Xanthomonas pathogens. Phylogenetic analysis revealed that this pathogen is very close to the tomato bacterial spot pathogen X. campestris pv. vesicatoria 85-10, with a completely different host range. We also compared X. axonopodis pv. citrumelo to the genome of citrus canker pathogen X. axonopodis pv. citri 306. Comparative genomic analysis showed differences in several gene clusters, like those for type III effectors, the type IV secretion system, lipopolysaccharide synthesis, and others. In addition to pthA, effectors such as xopE3, xopAI, and hrpW were absent from X. axonopodis pv. citrumelo while present in X. axonopodis pv. citri. These effectors might be responsible for survival and the low virulence of this pathogen on citrus compared to that of X. axonopodis pv. citri. We also identified unique effectors in X. axonopodis pv. citrumelo that may be related to the different host range as compared to that of X. axonopodis pv. citri. X. axonopodis pv. citrumelo also lacks various genes, such as syrE1, syrE2, and RTX toxin family genes, which were present in X. axonopodis pv. citri. These may be associated with the distinct virulences of X. axonopodis pv. citrumelo and X. axonopodis pv. citri. Comparison of the complete genome sequence of X. axonopodis pv. citrumelo to those of X. axonopodis pv. citri and X. campestris pv. vesicatoria provides valuable insights into the mechanism of bacterial virulence and host specificity.
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Affiliation(s)
- Neha Jalan
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850
| | - Valente Aritua
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850
| | - Dibyendu Kumar
- Interdisciplinary Center for Biotechnology Research, 2033 Mowry Road, University of Florida, Gainesville, Florida 32611
| | - Fahong Yu
- Interdisciplinary Center for Biotechnology Research, 2033 Mowry Road, University of Florida, Gainesville, Florida 32611
| | - Jeffrey B. Jones
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611
| | - James H. Graham
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850
| | - João C. Setubal
- Virginia Bioinformatics Institute and Department of Computer Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060-0477
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850
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20
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Pfander C, Anar B, Schwach F, Otto TD, Brochet M, Volkmann K, Quail MA, Pain A, Rosen B, Skarnes W, Rayner JC, Billker O. A scalable pipeline for highly effective genetic modification of a malaria parasite. Nat Methods 2011; 8:1078-82. [PMID: 22020067 PMCID: PMC3431185 DOI: 10.1038/nmeth.1742] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 09/29/2011] [Indexed: 11/08/2022]
Abstract
In malaria parasites, the systematic experimental validation of drug and vaccine targets by reverse genetics is constrained by the inefficiency of homologous recombination and by the difficulty of manipulating adenine and thymine (A+T)-rich DNA of most Plasmodium species in Escherichia coli. We overcame these roadblocks by creating a high-integrity library of Plasmodium berghei genomic DNA (>77% A+T content) in a bacteriophage N15-based vector that can be modified efficiently using the lambda Red method of recombineering. We built a pipeline for generating P. berghei genetic modification vectors at genome scale in serial liquid cultures on 96-well plates. Vectors have long homology arms, which increase recombination frequency up to tenfold over conventional designs. The feasibility of efficient genetic modification at scale will stimulate collaborative, genome-wide knockout and tagging programs for P. berghei.
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21
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Pinto UM, Flores-Mireles AL, Costa ED, Winans SC. RepC protein of the octopine-type Ti plasmid binds to the probable origin of replication within repC and functions only in cis. Mol Microbiol 2011; 81:1593-606. [PMID: 21883520 DOI: 10.1111/j.1365-2958.2011.07789.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Vegetative replication and partitioning of many plasmids and some chromosomes of alphaproteobacteria are directed by their repABC operons. RepA and RepB proteins direct the partitioning of replicons to daughter cells, while RepC proteins are replication initiators, although they do not resemble any characterized replication initiation protein. Here we show that the replication origin of an Agrobacterium tumefaciens Ti plasmid resides fully within its repC gene. Purified RepC bound to a site within repC with moderate affinity, high specificity and with twofold cooperativity. The binding site was localized to an AT-rich region that contains a large number of GANTC sites, which have been implicated in replication regulation in related organisms. A fragment of RepC containing residues 26-158 was sufficient to bind DNA, although with limited sequence specificity. This portion of RepC is predicted to have structural homology to members of the MarR family of transcription factors. Overexpression of RepC in A. tumefaciens caused large increases in copy number in cis but did not change the copy number of plasmids containing the same oriV sequence in trans, confirming other observations that RepC functions only in cis.
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Affiliation(s)
- Uelinton M Pinto
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
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22
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Chen Q, Narayanan K. Crude protein extraction protocol for phage N15 protelomerase in vitro enzymatic assays. Anal Biochem 2011; 414:169-71. [DOI: 10.1016/j.ab.2011.03.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Revised: 03/04/2011] [Accepted: 03/04/2011] [Indexed: 10/18/2022]
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23
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Ravin NV. N15: the linear phage-plasmid. Plasmid 2010; 65:102-9. [PMID: 21185326 DOI: 10.1016/j.plasmid.2010.12.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 12/14/2010] [Accepted: 12/17/2010] [Indexed: 11/24/2022]
Abstract
The lambdoid phage N15 of Escherichia coli is very unusual among temperate phages in that its prophage is not integrated into chromosome but is a linear plasmid molecule with covalently closed ends. Upon infection the phage DNA circularises via cohesive ends, then phage-encoded enzyme, protelomerase, cuts at an inverted repeat site and forms hairpin ends (telomeres) of the linear plasmid prophage. Replication of the N15 prophage is initiated at an internally located ori site and proceeds bidirectionally resulting in formation of duplicated telomeres. Then the N15 protelomerase cuts duplicated telomeres generating two linear plasmid molecules with hairpin telomeres. Stable inheritance of the plasmid prophage is ensured by partitioning operon similar to the F factor sop operon. Unlike F sop, the N15 centromere consists of four inverted repeats dispersed in the genome. The multiplicity and dispersion of centromeres are required for efficient partitioning of a linear plasmid. The centromeres are located in N15 genome regions involved in phage replication and control of lysogeny, and binding of partition proteins at these sites regulates these processes. Two N15-related lambdoid Siphoviridae phages, φKO2 in Klebsiella oxytoca and pY54 in Yersinia enterocolitica, also lysogenize their hosts as linear plasmids, as well as Myoviridae marine phages VP882 and VP58.5 in Vibrio parahaemolyticus and ΦHAP-1 in Halomonas aquamarina. The genomes of all these phages contain similar protelomerase genes, lysogeny modules and replication genes, as well as plasmid-partitioning genes, suggesting that these phages may belong to a group diverged from a common ancestor.
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Affiliation(s)
- Nikolai V Ravin
- Centre "Bioengineering", Russian Academy of Sciences, Prosp. 60-let Oktiabria, bld. 7-1, Moscow 117312, Russia.
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24
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Briffotaux J, Kobryn K. Preventing broken Borrelia telomeres: ResT couples dual hairpin telomere formation with product release. J Biol Chem 2010; 285:41010-8. [PMID: 20952394 DOI: 10.1074/jbc.m110.150060] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spirochetes of the genus Borrelia include the tick-transmitted causative agents of Lyme disease and relapsing fever. They possess unusual genomes composed mainly of linear replicons terminated by closed DNA hairpins. Hairpin telomeres are formed from inverted repeat replicated telomere junctions (rTels) by the telomere resolvase ResT. ResT uses a reaction mechanism similar to that of the type IB topoisomerases and tyrosine recombinases. ResT can catalyze three distinct reactions: telomere resolution, telomere fusion, and Holliday junction (HJ) formation. HJ formation is known to occur only in the context of a synapsed pair of rTels. To test whether telomere resolution was synapsis-dependent, we performed experiments with rTel substrates immobilized on streptavidin-coated beads. We report that telomere resolution by ResT is synapsis-independent, indicating that alternative complexes are formed for telomere resolution and HJ formation. We also present evidence that dual hairpin telomere formation precedes product release. This mechanism of telomere resolution prevents the appearance of broken telomeres. We compare and contrast this mechanism with that proposed for TelK, the telomere resolvase of ϕKO2.
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Affiliation(s)
- Julien Briffotaux
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
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25
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Dorokhov B, Ravin N, Lane D. On the role of centromere dispersion in stability of linear bacterial plasmids. Plasmid 2010; 64:51-9. [PMID: 20403379 DOI: 10.1016/j.plasmid.2010.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 04/08/2010] [Accepted: 04/12/2010] [Indexed: 11/26/2022]
Abstract
The N15 prophage-plasmid is linear, and the four centromere sites that enable its active partition are scattered rather than confined to a tandem array. This unusual arrangement suggested that the two features might be linked: centromere dispersion could enable condensation of linear DNA through interaction of partition complexes and so facilitate movement of segregating plasmid molecules. The present study examines this possibility. Linear N15 derivatives varying in centromere-site (IR) position, number and spacing were constructed, and stabilization of these plasmids by N15 SopAB proteins was measured. Stabilization increased in proportion to the number of IR sites and the distance between IR sites, the result expected if condensation mediated by partition complexes (SopB-IR) improves efficiency of SopA-directed segregation. However, visualization of two IR sites on the same molecule revealed that their colocalization did not depend on SopB but resulted from spontaneous folding of the linear DNA. Segregation of these sites by SopA was limited and incomplete compared to partition of plasmid copies. These observations imply that forces responsible for intrinsic folding of linear DNA tend to counter attempts to partition centromeres in cis to each other. We suggest that the beneficial effects of IR number and spacing on partition stem not from condensation but from provision of more numerous and better arranged substrates for SopA action.
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Affiliation(s)
- Boris Dorokhov
- Centre Bioengineering, Russian Academy of Sciences, Moscow 117312, Russia
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26
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Godiska R, Mead D, Dhodda V, Wu C, Hochstein R, Karsi A, Usdin K, Entezam A, Ravin N. Linear plasmid vector for cloning of repetitive or unstable sequences in Escherichia coli. Nucleic Acids Res 2010; 38:e88. [PMID: 20040575 PMCID: PMC2847241 DOI: 10.1093/nar/gkp1181] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 12/02/2009] [Accepted: 12/02/2009] [Indexed: 01/26/2023] Open
Abstract
Despite recent advances in sequencing, complete finishing of large genomes and analysis of novel proteins they encode typically require cloning of specific regions. However, many of these fragments are extremely difficult to clone in current vectors. Superhelical stress in circular plasmids can generate secondary structures that are substrates for deletion, particularly in regions that contain numerous tandem or inverted repeats. Common vectors also induce transcription and translation of inserted fragments, which can select against recombinant clones containing open reading frames or repetitive DNA. Conversely, transcription from cloned promoters can interfere with plasmid stability. We have therefore developed a novel Escherichia coli cloning vector (termed 'pJAZZ' vector) that is maintained as a linear plasmid. Further, it contains transcriptional terminators on both sides of the cloning site to minimize transcriptional interference between vector and insert. We show that this vector stably maintains a variety of inserts that were unclonable in conventional plasmids. These targets include short nucleotide repeats, such as those of the expanded Fragile X locus, and large AT-rich inserts, such as 20-kb segments of genomic DNA from Pneumocystis, Plasmodium, Oxytricha or Tetrahymena. The pJAZZ vector shows decreased size bias in cloning, allowing more uniform representation of larger fragments in libraries.
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Affiliation(s)
- Ronald Godiska
- Lucigen Corp., 2120 W. Greenview Dr., Middleton, WI 53562, USA.
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27
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Conversion of Linear DNA with Hairpin Telomeres into a Circular Molecule in the Course of Phage N15 Lytic Replication. J Mol Biol 2009; 391:261-8. [DOI: 10.1016/j.jmb.2009.06.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Revised: 06/03/2009] [Accepted: 06/05/2009] [Indexed: 11/23/2022]
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28
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The linear plasmid prophage Vp58.5 of Vibrio parahaemolyticus is closely related to the integrating phage VHML and constitutes a new incompatibility group of telomere phages. J Virol 2009; 83:9313-20. [PMID: 19587034 DOI: 10.1128/jvi.00672-09] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio parahaemolyticus O3:K6 pandemic strains recovered in Chile frequently possess a 42-kb plasmid which is the prophage of a myovirus. We studied the prototype phage VP58.5 and show that it does not integrate into the host cell chromosome but replicates as a linear plasmid (Vp58.5) with covalently closed ends (telomeres). The Vp58.5 replicon coexists with other plasmid prophages (N15, PY54, and PhiKO2) in the same cell and thus belongs to a new incompatibility group of telomere phages. We determined the complete nucleotide sequence (42,612 nucleotides) of the VP58.5 phage DNA and compared it with that of the plasmid prophage. The two molecules share the same nucleotide sequence but are 35% circularly permuted to each other. In contrast to the hairpin ends of the plasmid, VP58.5 phage DNA contains 5'-protruding ends. The VP58.5 sequence is 92% identical to the sequence of phage VHML, which was reported to integrate into the host chromosome. However, the gene order and termini of the phage DNAs are different. The VHML genome exhibits the same gene order as does the Vp58.5 plasmid. VHML phage DNA has been reported to contain terminal inverted repeats. This repetitive sequence is similar to the telomere resolution site (telRL) of VP58.5 which, after processing by the phage protelomerase, forms the hairpin ends of the Vp58.5 prophage. It is discussed why these closely related phages may be so different in terms of their genome ends and their lifestyle.
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29
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Kobryn K, Briffotaux J, Karpov V. Holliday junction formation by theBorrelia burgdorferitelomere resolvase, ResT: implications for the origin of genome linearity. Mol Microbiol 2009; 71:1117-30. [DOI: 10.1111/j.1365-2958.2008.06584.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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30
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Schroeder DC, Park Y, Yoon HM, Lee YS, Kang SW, Meints RH, Ivey RG, Choi TJ. Genomic analysis of the smallest giant virus--Feldmannia sp. virus 158. Virology 2009; 384:223-32. [PMID: 19054537 DOI: 10.1016/j.virol.2008.10.040] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Revised: 10/08/2008] [Accepted: 10/29/2008] [Indexed: 10/21/2022]
Abstract
Genomic analysis of Feldmannia sp. virus 158, the second phaeovirus to be sequenced in its entirety, provides further evidence that large double-stranded DNA viruses share similar evolutionary pressures as cellular organisms. Reductive evolution is clearly evident within the phaeoviruses which occurred via several routes: the loss of genes from an ancestral virus core genome most likely through genetic drift; and as a result of relatively large recombination events that caused wholesale loss of genes. The entire genome is 154,641 bp in length and has 150 predicted coding sequences of which 87% have amino acid sequence similarities to other algal virus coding sequences within the family Phycodnaviridae. Significant similarities were found, for thirty eight coding sequences (25%), to genes in gene databanks that are known to be involved in processes that include DNA replication, DNA methylation, signal transduction, viral integration and transposition, and protein-protein interactions. Unsurprisingly, the greatest similarity was observed between the two known viruses that infect Feldmannia, indicating the taxonomic linkage of these two viruses with their hosts. Moreover, comparative analysis of phycodnaviral genomic sequences revealed the smallest set of core genes (10 out of a possible 31) required to make a functional nucleocytoplasmic large dsDNA virus.
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31
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Schroeder BC, Cheng T, Jan YN, Jan LY. Expression cloning of TMEM16A as a calcium-activated chloride channel subunit. Cell 2008; 134:1019-29. [PMID: 18805094 PMCID: PMC2651354 DOI: 10.1016/j.cell.2008.09.003] [Citation(s) in RCA: 924] [Impact Index Per Article: 57.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Revised: 09/03/2008] [Accepted: 09/03/2008] [Indexed: 02/02/2023]
Abstract
Calcium-activated chloride channels (CaCCs) are major regulators of sensory transduction, epithelial secretion, and smooth muscle contraction. Other crucial roles of CaCCs include action potential generation in Characean algae and prevention of polyspermia in frog egg membrane. None of the known molecular candidates share properties characteristic of most CaCCs in native cells. Using Axolotl oocytes as an expression system, we have identified TMEM16A as the Xenopus oocyte CaCC. The TMEM16 family of "transmembrane proteins with unknown function" is conserved among eukaryotes, with family members linked to tracheomalacia (mouse TMEM16A), gnathodiaphyseal dysplasia (human TMEM16E), aberrant X segregation (a Drosophila TMEM16 family member), and increased sodium tolerance (yeast TMEM16). Moreover, mouse TMEM16A and TMEM16B yield CaCCs in Axolotl oocytes and mammalian HEK293 cells and recapitulate the broad CaCC expression. The identification of this new family of ion channels may help the development of CaCC modulators for treating diseases including hypertension and cystic fibrosis.
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Affiliation(s)
- Björn Christian Schroeder
- Department of Physiology, Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA 94143, USA
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32
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Abstract
repABC plasmids are widely distributed among alpha-proteobacteria. They are especially common in Rhizobiales. Some strains of this bacterial order can contain multiple repABC replicons indicating that this plasmid family includes several incompatibility groups. The replication and stable maintenance of these replicons depend on the presence of a repABC operon. The repABC operons sequenced to date share some general characteristics. All of them contain at least three protein-encoding genes: repA, repB and repC. The first two genes encode proteins involved in plasmid segregation, whereas repC encodes a protein crucial for replication. The origin of replication maps within the repC gene. In contrast, the centromere-like sequence (parS) can be located at various positions in the operon. In this review we will summarize current knowledge about this plasmid family, with special emphasis on their structural diversity and their complex genetic regulation. Finally, we will examine some ideas about their evolutionary origin and trends.
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Aihara H, Huang WM, Ellenberger T. An interlocked dimer of the protelomerase TelK distorts DNA structure for the formation of hairpin telomeres. Mol Cell 2007; 27:901-13. [PMID: 17889664 PMCID: PMC2041798 DOI: 10.1016/j.molcel.2007.07.026] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 06/11/2007] [Accepted: 07/25/2007] [Indexed: 12/27/2022]
Abstract
The termini of linear chromosomes are protected by specialized DNA structures known as telomeres that also facilitate the complete replication of DNA ends. The simplest type of telomere is a covalently closed DNA hairpin structure found in linear chromosomes of prokaryotes and viruses. Bidirectional replication of a chromosome with hairpin telomeres produces a catenated circular dimer that is subsequently resolved into unit-length chromosomes by a dedicated DNA cleavage-rejoining enzyme known as a hairpin telomere resolvase (protelomerase). Here we report a crystal structure of the protelomerase TelK from Klebsiella oxytoca phage varphiKO2, in complex with the palindromic target DNA. The structure shows the TelK dimer destabilizes base pairing interactions to promote the refolding of cleaved DNA ends into two hairpin ends. We propose that the hairpinning reaction is made effectively irreversible by a unique protein-induced distortion of the DNA substrate that prevents religation of the cleaved DNA substrate.
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Affiliation(s)
- Hideki Aihara
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8231, St. Louis, MO 63110
| | - Wai Mun Huang
- Department of Pathology, EEJ Medical Research Building, Room 5200B 15 N. Medical Dr. East, University of Utah Health Sciences Center, Salt Lake City, Utah 84112
| | - Tom Ellenberger
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8231, St. Louis, MO 63110
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34
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Mardanov AV, Strakhova TS, Smagin VA, Ravin NV. Tightly regulated, high-level expression from controlled copy number vectors based on the replicon of temperate phage N15. Gene 2007; 395:15-21. [PMID: 17433573 DOI: 10.1016/j.gene.2006.12.036] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 12/25/2006] [Accepted: 12/28/2006] [Indexed: 11/29/2022]
Abstract
A new Escherichia coli host/vector system has been developed to allow a dual regulation of both the plasmid copy number and gene expression. The new pN15E vectors are low copy number plasmids based on the replicon of temperate phage N15, comprising the repA replicase gene and cB repressor gene, controlling the plasmid copy number. Regulation of pN15E copy number is achieved through arabinose-inducible expression of phage N15 antirepressor protein, AntA, whose gene was integrated into the chromosome of the host strain under control of the PBAD promoter. The host strain also carried phage N15 partition operon, sop, allowing stable inheritance of pN15E vectors in the absence of selection pressure. In the first vector, pN15E4, the same PBAD promoter controls expression of a cloned gene. The second vector, pN15E6, carries the phage T5 promoter with a double lac operator repression module thus allowing independent regulation of promoter activity and copy number. Using the lacZ gene to monitor expression in these vectors, we show that the ratio of induction/repression can be about 7600-fold for pN15E4 and more than 15,000-fold for pN15E6. The low copy number of these vectors ensures very low basal level of expression allowing cloning genes encoding toxic products that was demonstrated by the stable maintenance of a gene encoding a restriction endonuclease in pN15E4. The tight control of transcription and the potential to regulate gene activities quantitatively over wide ranges will open up new approaches in the study of gene function in vivo and controlled expression of heterologous genes.
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35
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Mardanov AV, Ravin NV. Initiator protein DnaA of Escherichia coli is a negative replication regulator of linear phage-plasmid N15. RUSS J GENET+ 2007. [DOI: 10.1134/s1022795407010061] [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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36
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37
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Abstract
Bacteriophages (prokaryotic viruses) are favourite model systems to study DNA replication in prokaryotes, and provide examples for every theoretically possible replication mechanism. In addition, the elucidation of the intricate interplay of phage-encoded replication factors with 'host' factors has always advanced the understanding of DNA replication in general. Here we review bacteriophage replication based on the long-standing observation that in most known phage genomes the replication genes are arranged as modules. This allows us to discuss established model systems--f1/fd, phiX174, P2, P4, lambda, SPP1, N15, phi29, T7 and T4--along with those numerous phages that have been sequenced but not studied experimentally. The review of bacteriophage replication mechanisms and modules is accompanied by a compendium of replication origins and replication/recombination proteins (available as supplementary material online).
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38
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Sinyashina LN, Karataev GI. Molecular evidence for the lysogenic state of microorganisms belonging to the genus Bordetella and characterization of Bordetella parapertussis temperate bacteriophage 662-2. RUSS J GENET+ 2006. [DOI: 10.1134/s1022795406030057] [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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39
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Abstract
Spirochetes of the genus Borrelia have a highly unusual genome structure composed of over 20 replicons. Most of these replicons are linear and terminated by covalently closed hairpin ends or telomeres. Moreover, the linear replicons are affected by extensive DNA rearrangements, including telomere exchanges, DNA duplications, and harbour a large number of pseudogenes. The mechanism for the unusual genome plasticity in the linear replicons has remained elusive. The enzymatic machinery (the telomere resolvase ResT) responsible for generating the hairpin ends from replicative intermediates has recently been shown to also perform a reverse reaction that fuses telomeres on unrelated replicons. Infrequent stabilization of such fusion events over evolutionary time provides the first proposed biochemical mechanism for the DNA rearrangements that are so prominent in the linear replicons of B. burgdorferi.
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Affiliation(s)
- George Chaconas
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
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40
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Mardanov AV, Ravin NV. Functional characterization of the repA replication gene of linear plasmid prophage N15. Res Microbiol 2005; 157:176-83. [PMID: 16129583 DOI: 10.1016/j.resmic.2005.06.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 05/25/2005] [Accepted: 06/14/2005] [Indexed: 11/20/2022]
Abstract
The prophage of coliphage N15 is not integrated into the chromosome, but exists as a linear plasmid molecule with covalently closed ends. The only phage gene required for replication of circular N15 miniplasmids is repA (gene 37). Here we show that RepA-driven replication of the N15-based circular and linear miniplasmids is independent of host DnaB helicase protein, but requires the host DnaG primase. Replication of phage N15 DNA during lytic growth following infection does not depend on either DnaG or DnaB, but DnaG is required for lytic development after induction of the N15 lysogen. Finally, protein sequence analysis and replication data using different mutant strains suggest that RepA protein combines helicase and primase functions.
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Affiliation(s)
- Andrey V Mardanov
- Centre "Bioengineering", Russian Academy of Sciences, Prosp. 60-let Oktiabria, bld. 7-1, Moscow 117312, Russia
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41
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Ziegelin G, Tegtmeyer N, Lurz R, Hertwig S, Hammerl J, Appel B, Lanka E. The repA gene of the linear Yersinia enterocolitica prophage PY54 functions as a circular minimal replicon in Escherichia coli. J Bacteriol 2005; 187:3445-54. [PMID: 15866931 PMCID: PMC1111997 DOI: 10.1128/jb.187.10.3445-3454.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Yersinia enterocolitica prophage PY54 replicates as a linear DNA molecule with covalently closed ends. For replication of a circular PY54 minimal replicon that has been derived from a linear minireplicon, two phage-encoded loci are essential in Escherichia coli: (i) the reading frame of the replication initiation gene repA and (ii) its 212-bp origin located within the 3' portion of repA. The RepA protein acts in trans on the origin since we have physically separated the PY54 origin and repA onto a two-plasmid origin test system. For this trans action, the repA 3' end carrying the origin is dispensable. Mutagenesis by alanine scan demonstrated that the motifs for primase and for nucleotide binding present in the protein are essential for RepA activity. The replication initiation functions of RepA are replicon specific. The replication initiation proteins DnaA, DnaG, and DnaB of the host are unable to promote origin replication in the presence of mutant RepA proteins that carry single residue exchanges in these motifs. The proposed origins of the known related hairpin prophages PY54, N15, and PKO2 are all located toward the 3' end of the corresponding repA genes, where several structure elements are conserved. Origin function depends on the integrity of these elements.
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42
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Kobryn K, Burgin AB, Chaconas G. Uncoupling the chemical steps of telomere resolution by ResT. J Biol Chem 2005; 280:26788-95. [PMID: 15917226 DOI: 10.1074/jbc.m504530200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
ResT is the telomere resolvase of the spirochete Borrelia burgdorferi, the causative agent of Lyme disease. ResT is an essential cellular function that processes replication intermediates to produce linear replicons terminated by covalently closed hairpin telomeres. ResT generates these hairpin telomeres in a reaction with mechanistic similarities to those catalyzed by type IB topoisomerases and tyrosine recombinases. We report here, that like most of the tyrosine recombinases, ResT requires interprotomer communication, likely in an in-line synapse, to activate reaction chemistry. Unlike the tyrosine recombinases, however, we infer that the cleavage and strand transfer reactions on the two sides of the replicated telomere occur nearly simultaneously. Nonetheless, the chemical steps of the forward and reverse reactions performed by ResT can occur in a non-concerted fashion (i.e. events on the two sides of the replicated telomere can occur independently). We propose that uncoupling of reaction completion on the two sides of the substrate is facilitated by an early commitment to hairpin formation that is imposed by the precleavage action of the hairpin binding module of the ResT active site.
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Affiliation(s)
- Kerri Kobryn
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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43
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Kobryn K, Chaconas G. Fusion of hairpin telomeres by the B. burgdorferi telomere resolvase ResT implications for shaping a genome in flux. Mol Cell 2005; 17:783-91. [PMID: 15780935 DOI: 10.1016/j.molcel.2005.02.025] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2004] [Revised: 02/17/2005] [Accepted: 02/22/2005] [Indexed: 11/15/2022]
Abstract
Spirochetes of the genus Borrelia include the causative agents of Lyme disease and relapsing fever. These bacteria have a highly segmented genome where most replicons are linear molecules terminated by covalently closed hairpin telomeres. Moreover, these genomes appear to be in a state of flux with extensive and ongoing DNA rearrangements by unknown mechanisms. The B. burgdorferi telomere resolvase ResT generates the hairpin telomeres from replication intermediates in a reaction with mechanistic similarities to that catalyzed by type IB topoisomerases and tyrosine recombinases. We report here the unexpected ability of ResT to catalyze the fusion of hairpin telomeres in a reversal of the telomere resolution reaction. We propose that stabilized ResT-mediated telomere fusions are an underlying force for maintaining the B. burgdorferi genome in a state of flux.
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Affiliation(s)
- Kerri Kobryn
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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44
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Kropinski AM, Hayward M, Agnew MD, Jarrell KF. The genome of BCJA1c: a bacteriophage active against the alkaliphilic bacterium, Bacillus clarkii. Extremophiles 2004; 9:99-109. [PMID: 15841342 DOI: 10.1007/s00792-004-0425-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Accepted: 09/17/2004] [Indexed: 10/26/2022]
Abstract
The sequence of the genome of the first alkaliphilic bacteriophage has been determined. Temperate phage BCJA1 possesses a terminally redundant genome of approximately 41 kb, with a mol% G + C content of 41.7 and 59 genes arranged predominantly into two divergent transcriptons. The integrase gene of this phage is unique in that it contains a ribosomal slippage site. While this type of translational regulation occurs in the synthesis of transposase, this is the first time that it has been observed in a bacteriophage integrase. The DNA replication, recombination, packaging, and morphogenesis proteins show their greatest sequence similarity to phages and prophages from the genus Streptococcus. Host specificity, lysin, and lysogeny maintenance functions are most closely related to genes from Bacillus species.
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Affiliation(s)
- Andrew M Kropinski
- Department of Microbiology and Immunology, Queens University, Kingston, ON, K7L 3N6, Canada.
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45
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Deneke J, Burgin AB, Wilson SL, Chaconas G. Catalytic residues of the telomere resolvase ResT: a pattern similar to, but distinct from, tyrosine recombinases and type IB topoisomerases. J Biol Chem 2004; 279:53699-706. [PMID: 15471873 DOI: 10.1074/jbc.m409001200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ResT is a member of the telomere resolvases, a newly discovered class of DNA breakage and reunion enzymes. These enzymes are involved in the formation of co-valently closed hairpin DNA ends that are found in linear prokaryotic chromosomes and plasmids. The hairpins are generated by telomere resolution, where the replicated linear DNA ends are processed by DNA breakage followed by joining of DNA free ends to the complementary strand of the same molecule. Previous studies have shown that ResT catalyzes hairpin formation through a two-step transesterification similar to tyrosine recombinases and type IB topoisomerases. In the present study we have probed the reaction mechanism of ResT. The enzyme was found to efficiently utilize a substrate with a 5'-bridging phosphorothiolate at each cleavage site, similar to tyrosine recombinases/type IB topoisomerases. Using such a substrate to trap the covalent protein-DNA intermediate, coupled with affinity purification and mass spectroscopy, we report a new, non-radioactive approach to directly determine the position of the amino acid in the protein, which is linked to the DNA. We report that tyrosine 335 is the active site nucleophile in ResT, strengthening the link between ResT and tyrosine recombinases/type IB topoisomerases. However, a distinct pattern of catalytic residues with similarities, but distinct differences from the above enzymes was suggested. The differences include the apparent absence of a general acid catalyst, as well as the dispensability of the final histidine in the RKHRHY hexad. Finally, two signature motifs (GRR(2X)E(6X)F and LGH(4-6X)T(3X)Y) near the catalytic residues of aligned telomere resolvases are noted.
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Affiliation(s)
- Jan Deneke
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta T2N 1N4, Canada
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46
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Bankhead T, Chaconas G. Mixing active-site components: a recipe for the unique enzymatic activity of a telomere resolvase. Proc Natl Acad Sci U S A 2004; 101:13768-73. [PMID: 15365172 PMCID: PMC518831 DOI: 10.1073/pnas.0405762101] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Indexed: 11/18/2022] Open
Abstract
The ResT protein, a telomere resolvase from Borrelia burgdorferi, processes replication intermediates into linear replicons with hairpin ends by using a catalytic mechanism similar to that for tyrosine recombinases and type IB topoisomerases. We have identified in ResT a hairpin binding region typically found in cut-and-paste transposases. We show that substitution of residues within this region results in a decreased ability of these mutants to catalyze telomere resolution. However, the mutants are capable of resolving heteroduplex DNA substrates designed to allow spontaneous destabilization and prehairpin formation. These findings support the existence of a hairpin binding region in ResT, the only known occurrence outside a transposase. The combination of transposase-like and tyrosine-recombinase-like domains found in ResT indicates the use of a composite active site and helps explain the unique breakage-and-reunion reaction observed with this protein. Comparison of the ResT sequence with other known telomere resolvases suggests that a hairpin binding motif is a common feature in this class of enzyme; the sequence motif also appears in the RAG recombinases. Finally, our data support a mechanism of action whereby ResT induces prehairpin formation before the DNA cleavage step.
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Affiliation(s)
- Troy Bankhead
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada T2N 4N1
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47
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Casjens SR, Gilcrease EB, Huang WM, Bunny KL, Pedulla ML, Ford ME, Houtz JM, Hatfull GF, Hendrix RW. The pKO2 linear plasmid prophage of Klebsiella oxytoca. J Bacteriol 2004; 186:1818-32. [PMID: 14996813 PMCID: PMC355964 DOI: 10.1128/jb.186.6.1818-1832.2004] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2003] [Accepted: 12/10/2003] [Indexed: 11/20/2022] Open
Abstract
Temperate bacteriophages with plasmid prophages are uncommon in nature, and of these only phages N15 and PY54 are known to have a linear plasmid prophage with closed hairpin telomeres. We report here the complete nucleotide sequence of the 51,601-bp Klebsiella oxytoca linear plasmid pKO2, and we demonstrate experimentally that it is also a prophage. We call this bacteriophage phiKO2. An analysis of the 64 predicted phiKO2 genes indicate that it is a fairly close relative of phage N15; they share a mosaic relationship that is typical of different members of double-stranded DNA tailed-phage groups. Although the head, tail shaft, and lysis genes are not recognizably homologous between these phages, other genes such as the plasmid partitioning, replicase, prophage repressor, and protelomerase genes (and their putative targets) are so similar that we predict that they must have nearly identical DNA binding specificities. The phiKO2 virion is unusual in that its phage lambda-like tails have an exceptionally long (3,433 amino acids) central tip tail fiber protein. The phiKO2 genome also carries putative homologues of bacterial dinI and umuD genes, both of which are involved in the host SOS response. We show that these divergently transcribed genes are regulated by LexA protein binding to a single target site that overlaps both promoters.
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Affiliation(s)
- Sherwood R Casjens
- Department of Pathology, University of Utah Medical School, Salt Lake City, Utah 84132, USA.
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