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Benita Y, Oosting RS, Lok MC, Wise MJ, Humphery-Smith I. Regionalized GC content of template DNA as a predictor of PCR success. Nucleic Acids Res 2003; 31:e99. [PMID: 12907751 PMCID: PMC169991 DOI: 10.1093/nar/gng101] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2003] [Revised: 06/08/2003] [Accepted: 06/27/2003] [Indexed: 11/15/2022] Open
Abstract
A set of 1438 human exons was subjected to nested PCR. The initial success rate using a standard PCR protocol required for ligation-independent cloning was 83.4%. Logistic regression analysis was conducted on 27 primer- and template-related characteristics, of which most could be ignored apart from those related to the GC content of the template. Overall GC content of the template was a good predictor for PCR success; however, specificity and sensitivity values for predicted outcome were improved to 84.3 and 94.8%, respectively, when regionalized GC content was employed. This represented a significant improvement in predictability with respect to GC content alone (P < 0.001; chi(2)) and is expected to increase in relative sensitivity as template size increases. Regionalized GC was calculated with respect to a threshold of 61% GC content and a sliding window of 21 bp across the target sequence. Fine-tuning of PCR conditions is not practicable for all target sequences whenever a large number of genes of different lengths and GC content are to be amplified in parallel, particularly if total open reading frame or domain coverage is essential for recombinant protein synthesis. Thus, the present method is proposed as a means of grouping subsets of genes possessing potentially difficult target sequences so that PCR conditions can be optimized separately in order to obtain improved outcomes.
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Affiliation(s)
- Yair Benita
- Department of Pharmaceutical Proteomics, Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, Utrecht, The Netherlands.
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52
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Choi SS, Lee JW, Kang BY, Ha NJ. Antimicrobial resistance patterns of vancomycin-resistant Streptococcus equinus isolated from animal foods and epidemiological typing of resistant S. equinus by microbial uniprimer kit. Arch Pharm Res 2003; 26:638-43. [PMID: 12967199 DOI: 10.1007/bf02976713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Raw milk samples, and cow and chicken intestines were tested to isolate vancomycin-resistant, gram-positive bacteria. From these samples, we isolated seven vancomycin-resistant Streptococcus equinus, two vancomycin-resistant viridans Streptococcus and two vancomycin-resistant Enterococcus faecium. The MICs of several antibiotics, including vancomycin, against these strains were tested. Seven isolates of S. equinus showed high level resistance to vancomycin and teicoplanin (>100 microg/mL). The cell wall thickness of these strains was compared with that of the sensitive strain by TEM and no differences were obserbed between these strains. We compared the strains of vancomycin-resistant Streptococcus equinus using PCR with Microbial Uniprimer Kit. We concluded that it is necessary to combine other methods in order to cluster and identify all isolates of S. equinus.
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Affiliation(s)
- Sung-Sook Choi
- Department of Food Science, Sahmyook College, Seoul 139-742, Korea
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53
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Jeong W, Kweon CH, Kang SW, Paik SG. Diagnosis and quantification of Theileria sergenti using TaqMan PCR. Vet Parasitol 2003; 111:287-95. [PMID: 12559708 DOI: 10.1016/s0304-4017(02)00388-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Theileria sergenti is the causative agent of persistent theileriosis in cattle. The ubiquitous infection of theileiriosis causes chronic anemia and fever in cattle, especially in exogenous cattle. In this study, we applied real-time polymerase chain reaction (PCR) for the diagnosis and quantification of parasite using specific primers for 33 kDa gene fragment of T. sergenti. Comparison of TaqMan PCR with traditional microscopic method, Giemsa's staining, on blood collected from cattle revealed the specificity up to 0.00005% of parasitemia to traditional diagnosis. In addition, it was found that this method can estimate the relative status of infection among herds. The results of present study showed that this method is not only applicable to detect the chronic infection of Theileria, but also effective in evaluation on parasitemia status of cattle, thus it can be used in monitoring the health status in field.
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Affiliation(s)
- Wooseog Jeong
- Bacteriology Division, Parasitology Laboratory, National Veterinary Research and Quarantine Service, Ministry of Agriculture and Forestry, # 480 Anyang-6-dong, Gyeonggi-do 427-824, Anyang-si, Republic of Korea.
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54
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Etokebe GE, Wiencke K, Haug T, Spurkland A. The use of modified primer competitors to enhance yields and specificity of HLA class I amplification by polymerase chain reaction (PCR). TISSUE ANTIGENS 2003; 61:172-6. [PMID: 12694586 DOI: 10.1034/j.1399-0039.2003.00011.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Various PCR based techniques have been developed for genomic HLA typing. The fidelity of these techniques is highly dependent upon the specificity of the primers for the given HLA locus. Due to the high degree of homology between HLA class I loci, few primer sites that selectively amplify genes at a given HLA class I locus may be identified. To avoid coamplification of homologous loci, we designed and applied primer competitors for PCR amplification of HLA-A, -B and -C loci. Primer competitors identical to the 3' end of the specific primers and completely degenerate in the 5' end were designed and titrated into the respective HLA-locus PCR mixtures. We found that inclusion of primer competitors in the PCR reaction increased the specificity and yields of HLA class I amplifications, in particular when crude DNA preparation was used as template. This was particularly true for DNA preparations of low quality. The method described here may be useful for various protocols for downstream genomic typing of HLA-A, -B and -C alleles. In particular the method is useful when DNA is in scarce supply (i.e., for extensive PCR based allelic typing) or when high yields and locus specificity of amplicons are needed (i.e., sequencing-based typing).
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Affiliation(s)
- G E Etokebe
- Institute of Immunology, National University Hospital, Oslo, Norway.
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55
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Goto RM, Afanassieff M, Ha J, Iglesias GM, Ewald SJ, Briles WE, Miller MM. Single-strand conformation polymorphism (SSCP) assays for major histocompatibility complex B genotyping in chickens. Poult Sci 2002; 81:1832-41. [PMID: 12512574 DOI: 10.1093/ps/81.12.1832] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have developed a DNA-based method for defining MHC B system genotypes in chickens. Genotyping by this method requires neither prior determination of allele-specific differences in nucleotide sequence nor the preparation of haplotype-specific alloantisera. Allelic differences at chicken B-F (class I) and B-L (class II) loci are detected in PCR single-strand conformation polymorphism (SSCP) assays. PCR primer pairs were designed to hybridize specifically with conserved sequences surrounding hypervariable regions within the two class I and two class I loci of the B-complex and used to generate DNA fragments that are heat- and formamide-denatured and then analyzed on nondenaturing polyacrylamide gels. PCR primer pairs were tested for the capacity to produce SSCP patterns allowing the seven B haplotypes in the MHC B congenic lines, and seven B haplotypes known to be segregating in two commercial broiler breeder lines to be distinguished. Primer pairs were further evaluated for their capacity to reveal the segregation of B haplotypes in a fully pedigreed family and in a closed population. Concordance was found between SSCP patterns and previously assigned MHC types. B-F and B-L SSCP patterns segregated in linkage as expected for these closely linked loci. We conclude that this method is valuable for defining MHC B haplotypes and for detecting potential recombinant haplotypes especially when used in combination with B-G (class IV) typing by restriction fragment pattern.
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Affiliation(s)
- R M Goto
- Division of Molecular Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA 91010, USA
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56
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Exner MM, Lewinski MA. Sensitivity of multiplex real-time PCR reactions, using the LightCycler and the ABI PRISM 7700 Sequence Detection System, is dependent on the concentration of the DNA polymerase. Mol Cell Probes 2002; 16:351-7. [PMID: 12477439 DOI: 10.1006/mcpr.2002.0433] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The introduction of multiplex PCR techniques to clinical laboratories has provided a means to streamline assays and to produce multiple results with minimal effort. While this methodology is very beneficial, care must be taken to ensure that reactions are properly optimized to allow for maximum sensitivity. This study was conducted to determine whether the sensitivity of multiplex-real-time PCR assays could be improved by increasing the concentration of DNA polymerase within a reaction. Multiplex reactions were designed to simultaneously detect the human HLA-DQ gene and a sequence from the UL83 region of the CMV genome. Two real-time PCR systems, one utilizing AmpliTaq Gold DNA polymerase and the ABI 7700 Sequence Detection System, and one utilizing FastStart Taq DNA polymerase and the Roche LightCycler were tested. The results indicated that increasing the AmpliTaq Gold concentration from 0.050 to 0.10 U/microl and the FastStart Taq concentration from 0.1875 to 0.375 U/microl increased detection sensitivity from 5,000 to 50 CMV copies per PCR reaction. In separate experiments, commercially prepared mastermixes were utilized for both real-time PCR platforms as per the manufacturer's suggestions or with the addition of supplemental DNA polymerase. In assays designed to detect 4 CMV genome copies per reaction, the addition of 2.5 U of AmpliTaq Gold to TaqMan Universal Mastermix increased the detection rate from 21 to 67%, and the addition of 5 U of FastStart Taq to FastStart DNA Master Hybridization Probes mastermix increased the detection rate from 17 to 56%. These results indicate that increasing the DNA polymerase concentration in multiplex real-time PCR reactions may be a simple way to optimize assay sensitivity.
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Affiliation(s)
- M M Exner
- Quest Diagnostics' Nichols Institute, San Juan Capistrano, CA 92690, USA.
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57
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Limansky AS, Viale AM. Can composition and structural features of oligonucleotides contribute to their wide-scale applicability as random PCR primers in mapping bacterial genome diversity? J Microbiol Methods 2002; 50:291-7. [PMID: 12031579 DOI: 10.1016/s0167-7012(02)00040-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Among current genotypic methodologies, random amplification of polymorphic DNA (RAPD or AP-PCR) represents a widely employed assay for the evaluation of bacterial genomic diversity. A common bottleneck of this technique, however, is represented by the screening of useful informative primers to discriminate among isolates of a particular bacterial species. In an attempt to simplify this process, we evaluated here the utility of degenerate oligonucleotides to act as informative AP-PCR primers. For this purpose, a number of features (G+C contents, degeneracy rate, modifications at the 5' end) of related degenerate primers was tested for their effects in the generation of informative arrays from a set of bacterial genomes. Our results indicate that a combination of a wide base composition and a common palindromic structure at the 5' end of the sequences that compose the degenerate primers tested here beneficially resulted for the generation of informative arrays aimed to evaluate the bacterial genome heterogeneity.
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Affiliation(s)
- Adriana S Limansky
- Instituto de Biología Molecular y Celular de Rosario (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000, Rosario, Argentina
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58
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Abstract
Real time RT-PCR is the most sensitive method for quantitation of gene expression levels. The accuracy can be dependent on the mathematical model on which the quantitative methods are based. The generally accepted mathematical model assumes that amplification efficiencies are equal at the exponential phase of the reactions for the same amplicon. However, no methods are available to test the assumptions regarding amplification efficiency before one starts the real time PCR quantitation. Here we further develop and test the validity of a new mathematical model which dynamically fits real time PCR data with good correlation (R(2)=0.9995+/-0.002, n=50). The method is capable of measuring cycle-by-cycle PCR amplification efficiencies and demonstrates that these change dynamically. Validation of the method revealed the intrinsic relationship between the initial amount of gene transcript and kinetic parameters. A new quantitative method is proposed which represents a simple but accurate quantitative method.
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Affiliation(s)
- Weihong Liu
- Department of Physiology, University of Adelaide, Adelaide, SA 5005, Australia
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59
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60
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von Ahsen N, Wittwer CT, Schütz E. Oligonucleotide Melting Temperatures under PCR Conditions: Nearest-Neighbor Corrections for Mg2+, Deoxynucleotide Triphosphate, and Dimethyl Sulfoxide Concentrations with Comparison to Alternative Empirical Formulas. Clin Chem 2001. [DOI: 10.1093/clinchem/47.11.1956] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Background: Many techniques in molecular biology depend on the oligonucleotide melting temperature (Tm), and several formulas have been developed to estimate Tm. Nearest-neighbor (N-N) models provide the highest accuracy for Tm prediction, but it is not clear how to adjust these models for the effects of reagents commonly used in PCR, such as Mg2+, deoxynucleotide triphosphates (dNTPs), and dimethyl sulfoxide (DMSO).
Methods: The experimental Tms of 475 matched or mismatched target/probe duplexes were obtained in our laboratories or were compiled from the literature based on studies using the same real-time PCR platform. This data set was used to evaluate the contributions of [Mg2+], [dNTPs], and [DMSO] in N-N calculations. In addition, best-fit coefficients for common empirical formulas based on GC content, length, and the equivalent sodium ion concentration of cations [Na+eq] were obtained by multiple regression.
Results: When we used [Na+eq] = [Monovalent cations] + 120($\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\sqrt{{[}Mg^{2{+}}{]}\ {-}\ {[}dNTPs{]}}\) \end{document}$) (the concentrations in this formula are mmol/L) to correct ΔS0 and a DMSO term of 0.75 °C (%DMSO), the SE of the N-N Tm estimate was 1.76 °C for perfectly matched duplexes (n = 217). Alternatively, the empirical formula Tm (°C) = 77.1 °C + 11.7 × log[Na+eq] + 0.41(%GC) − 528/bp − 0.75 °C(%DMSO) gave a slightly higher SE of 1.87 °C. When all duplexes (matched and mismatched; n = 475) were included in N-N calculations, the SE was 2.06 °C.
Conclusions: This robust model, accounting for the effects of Mg2+, DMSO, and dNTPs on oligonucleotide Tm in PCR, gives reliable Tm predictions using thermodynamic N-N calculations or empirical formulas.
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Affiliation(s)
- Nicolas von Ahsen
- Department of Clinical Chemistry, Georg-August University, Robert Koch Strasse 40, 37075 Goettingen, Germany
| | - Carl T Wittwer
- Department of Pathology, University of Utah Medical School, Salt Lake City, UT 84132
| | - Ekkehard Schütz
- Department of Clinical Chemistry, Georg-August University, Robert Koch Strasse 40, 37075 Goettingen, Germany
- Chronic Illness Research Foundation, San Francisco, CA 94107
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61
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Santos CB, Costa Lima MA, Pimentel MM. A new PCR assay useful for screening of FRAXE/FMR2 mental impairment among males. Hum Mutat 2001; 18:157-62. [PMID: 11462240 DOI: 10.1002/humu.1165] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
FRAXE (FMR2) is a fragile site associated with mental impairment located in Xq28, 600 kb distal to FRAXA (FMR1), the fragile X syndrome fragile site. The FRAXE mutation is an expansion of a CCG repeat that results in methylation of a nearby CpG island. FRAXE alleles could be divided into four categories: normal (6-30 CCG repeats), intermediate (31-60 CCG repeats), premutation (61-200 CCG repeats), and full mutation (over 200 repeats). We have developed a non-isotopic polymerase chain reaction (PCR)-based assay for the identification of FRAXE full mutation alleles among mentally impaired men. In this novel PCR test for the FRAXE locus, we used three primers to permit an amplification of a 223 bp monomorphic internal control fragment in addition to the amplification of a 419 bp (CCG)(16) FRAXE locus band. A linear series of 93 male patients referred for FRAXE testing but found to be negative for the (CCG)(n) expansion in the FMR2 gene by Southern blotting analysis were retested by our PCR technique. In addition, we analyzed two positive controls consisting of a FRAXE fully mutated male and one male with a Xq terminal deletion. The developed PCR test showed accuracy of 100% in the normal individuals retested by PCR analysis, as well as in the two positive control samples utilized, in which the strategy of multiplex amplification worked as expected. Although not suitable for medical diagnosis of females and mosaics, it constitutes an important strategy for PCR typing and for FRAXE population screening.
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Affiliation(s)
- C B Santos
- Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.
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62
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Abstract
PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.
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63
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Elnifro EM, Ashshi AM, Cooper RJ, Klapper PE. Multiplex PCR: optimization and application in diagnostic virology. Clin Microbiol Rev 2000; 13:559-70. [PMID: 11023957 PMCID: PMC88949 DOI: 10.1128/cmr.13.4.559] [Citation(s) in RCA: 353] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.
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Affiliation(s)
- E M Elnifro
- School of Medicine, The University of Manchester, Central Manchester Healthcare Trust, Manchester, United Kingdom
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64
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Moore GL, Maranas CD. Modeling DNA mutation and recombination for directed evolution experiments. J Theor Biol 2000; 205:483-503. [PMID: 10882567 DOI: 10.1006/jtbi.2000.2082] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Directed evolution experiments rely on the cyclical application of mutagenesis, screening and amplification in a test tube. They have led to the creation of novel proteins for a wide range of applications. However, directed evolution currently requires an uncertain, typically large, number of labor intensive and expensive experimental cycles before proteins with improved function are identified. This paper introduces predictive models for quantifying the outcome of the experiments aiding in the setup of directed evolution for maximizing the chances of obtaining DNA sequences encoding enzymes with improved activities. Two methods of DNA manipulation are analysed: error-prone PCR and DNA recombination. Error-prone PCR is a DNA replication process that intentionally introduces copying errors by imposing mutagenic reaction conditions. The proposed model calculates the probability of producing a specific nucleotide sequence after a number of PCR cycles. DNA recombination methods rely on the mixing and concatenation of genetic material from a number of parent sequences. This paper focuses on modeling a specific DNA recombination protocol, DNA shuffling. Three aspects of the DNA shuffling procedure are modeled: the fragment size distribution after random fragmentation by DNase I, the assembly of DNA fragments, and the probability of assembling specific sequences or combinations of mutations. Results obtained with the proposed models compare favorably with experimental data.
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Affiliation(s)
- G L Moore
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
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65
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Ryu KH, Choi SH, Lee JS. Restriction primers as short as 6-mers for PCR amplification of bacterial and plant genomic DNA and plant viral RNA. Mol Biotechnol 2000; 14:1-3. [PMID: 10911610 DOI: 10.1385/mb:14:1:01] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Amplification of DNA or RNA sequences using the polymerase chain reaction (PCR) or reverse transcriptase PCR (RT-PCR) requires primers of an appropriate length to be designed. Two hexamer restriction primers, denoted as E101 and H301, which correspond to sequences of EcoRI and HindIII recognition sites, respectively, were selected and used as primers in PCR and RT-PCR. We first applied the restriction primers to the plasmid DNA and bacterial (Pseudomonas) and plant (Cymbidium) genomic DNAs. We observed positive DNA amplifications with the recombinant plasmid DNA and bacterial and plant genomic DNAs. Purified viral RNA was used for template in the RT-PCR with the primers and successful DNA amplification was obtained. These results suggest that the 6-mer restriction primers can be useful for new applications in PCR.
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Affiliation(s)
- K H Ryu
- Department of Horticultural Science, College of Natural Science, Seoul Women's University, Korea.
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66
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Gaikwad A, Tewari KK, Kumar D, Chen W, Mukherjee SK. Isolation and characterisation of the cDNA encoding a glycosylated accessory protein of pea chloroplast DNA polymerase. Nucleic Acids Res 1999; 27:3120-9. [PMID: 10454608 PMCID: PMC148538 DOI: 10.1093/nar/27.15.3120] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cDNA encoding p43, a DNA binding protein from pea chloroplasts (ct) that binds to cognate DNA polymerase and stimulates the polymerase activity, has been cloned and characterised. The characteristic sequence motifs of hydroxyproline-rich glyco-proteins (HRGP) are present in the cDNA corres-ponding to the N-terminal domain of the mature p43. The protein was found to be highly O-arabinosylated. Chemically deglycosylated p43 (i.e. p29) retains its binding to both DNA and pea ct-DNA polymerase but fails to stimulate the DNA polymerase activity. The mature p43 is synthesised as a pre-p43 protein containing a 59 amino acid long transit peptide which undergoes stromal cleavage as evidenced from the post-translational in vitro import of the precursor protein into the isolated intact pea chloroplasts. Surprisingly, p43 is found only in pea chloroplasts. The unique features present in the cloned cDNA indicate that p43 is a novel member of the HRGP family of proteins. Besides p43, no other DNA-polymerase accessory protein with O-glycosylation has been reported yet.
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Affiliation(s)
- A Gaikwad
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110 067, India
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67
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Fagotti A, Gabbiani G, Pascolini R, Neuville P. Multiple isoform recovery (MIR)-PCR: a simple method for the isolation of related mRNA isoforms. Nucleic Acids Res 1998; 26:2031-3. [PMID: 9518500 PMCID: PMC147508 DOI: 10.1093/nar/26.8.2031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We present a rapid and efficient method for the detection of related transcripts with different expression levels. This approach combines the rapid amplification of cDNA ends (RACE) method with a cDNA subtractive technique. The strategy is based on successive subtractions of prevalent isoforms resulting in enrichment of less expressed transcripts. For each subtraction, a biotinylated primer specific for the prevalent isoform is hybridized on the total cDNA and the hybrid is retained on a streptavidin affinity column. The unbound cDNA serves as a template for subsequent isoform identification. To illustrate its application we describe the isolation of three new actin cDNA isoforms in the freshwater planarian Dugesia (S) polychroa.
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Affiliation(s)
- A Fagotti
- Institute of Comparative Anatomy, University of Perugia, Perugia, Italy
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68
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Luki N, Lebel P, Boucher M, Doray B, Turgeon J, Brousseau R. Comparison of polymerase chain reaction assay with culture for detection of genital mycoplasmas in perinatal infections. Eur J Clin Microbiol Infect Dis 1998; 17:255-63. [PMID: 9707308 DOI: 10.1007/bf01699982] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The polymerase chain reaction (PCR) technique was compared with culture for the detection of Ureaplasma urealyticum, Mycoplasma hominis, and Mycoplasma genitalium in clinical samples (vaginal secretions, throat and endotracheal secretions, and skin swabs) obtained from 47 high-risk pregnant women peripartum and eight newborn infants. Detection using PCR with homologous primers was highly specific, as a product with the expected length was consistently amplified with homologous but not with heterologous species. The limit of detection of the PCR assay was 10 color-changing units (CCU) of Mycoplasma strains. The PCR technique facilitated detection of Ureaplasma urealyticum DNA in 31 of 55 patients studied, of Mycoplasma hominis in seven samples, and of Mycoplasma genitalium in two samples. Four PCR-positive patients yielded culture-negative results. In one case a culture-positive sample was negative by PCR. The results show that PCR is a valuable tool for rapid detection of genital mycoplasmas in clinical samples. It is fast, sensitive, specific, and easy to perform, requiring minimal preparation of the clinical sample.
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Affiliation(s)
- N Luki
- Environmental Genetics Group, Biotechnology Research Institute, Montreal, Quebec, Canada
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69
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Sharma S, Brousseau R, Kasatiya S. Detection and confirmation of Mycoplasma pneumoniae in urogenital specimens by PCR. J Clin Microbiol 1998; 36:277-80. [PMID: 9431966 PMCID: PMC124853 DOI: 10.1128/jcm.36.1.277-280.1998] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Following the isolation of Mycoplasma pneumoniae from urogenital specimens (M. Goulet, R. Dular, J. G. Tully, G. Billows, and S. Kasatiya, J. Clin. Microbiol. 33:2823-2825, 1995), a study was undertaken to confirm the observations by PCR. Specific primers directed to the P1 adhesin gene of M. pneumoniae were used. A total of 300 genital specimens were tested for M. pneumoniae and Mycoplasma genitalium by culture and PCR. Of these, 15 were positive by culture and 17 were positive by PCR for M. pneumoniae. No M. genitalium was detected in any of the specimens by either method. The present study demonstrates that PCR is sensitive and rapid compared to cumbersome culture methods and can be used to detect M. pneumoniae in urogenital specimens in a routine diagnostic laboratory.
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Affiliation(s)
- S Sharma
- Ottawa Public Health Laboratory, Ontario, Canada
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70
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Rapid identification and detection of Lactobacillus sanfrancisco in sourdough by species-specific PCR with 16S rRNA-targeted primers. Syst Appl Microbiol 1997. [DOI: 10.1016/s0723-2020(97)80036-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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71
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Abstract
An increasing number of proteins are being identified that regulate gene expression by binding specific nucleic acidsin vivo. A method termed genomic SELEX facilitates the rapid identification of networks of protein-nucleic acid interactions by identifying within the genomic sequences of an organism the highest affinity sites for any protein of the organism. As with its progenitor, SELEX of random-sequence nucleic acids, genomic SELEX involves iterative binding, partitioning, and amplification of nucleic acids. The two methods differ in that the variable region of the nucleic acid library for genomic SELEX is derived from the genome of an organism. We have used a quick and simple method to construct Escherichia coli, Saccharomyces cerevisiae, and human genomic DNA PCR libraries that can be transcribed with T7 RNA polymerase. We present evidence that the libraries contain overlapping inserts starting at most of the positions within the genome, making these libraries suitable for genomic SELEX.
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Affiliation(s)
- B S Singer
- Department of Molecular Biology, University of Colorado, Boulder 80309-0347, USA
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72
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Heinemeyer T, Klingenhoff A, Hansen W, Schumacher L, Hauser H, Wirth M. A sensitive method for the detection of murine C-type retroviruses. J Virol Methods 1997; 63:155-65. [PMID: 9015286 DOI: 10.1016/s0166-0934(96)02124-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A RT-PCR assay was developed for group-specific detection of murine C-type retroviruses using a nested set of degenerated primers. To distinguish exogenous viruses from related, but silent endogenous viruses, a DNAse I pretreatment of supernatants is applied. This is followed by a heat inactivation/denaturation step. The PCR method is ultrasensitive. which enables the detection of 100 attogram of MoMuLV proviral DNA or up to 1-10 infectious mouse C-type retroviruses in 10 microl supernatant of infected cells. The high specificity of the method allows the differentiation between mouse C-type retroviruses and related retroviruses of the A, B, and D type and C-type retroviruses found in other species. It serves as a valuable tool for the screening of animal cell cultures for contaminations with mouse retroviruses, e.g. hybridomas or recombinant cell lines producing foreign proteins.
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Affiliation(s)
- T Heinemeyer
- Department of Regulation and Differentiation, Gesellschaft für Biotechnologische Forschung, Braunschweig, Germany
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73
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Rochelle PA, De Leon R, Stewart MH, Wolfe RL. Comparison of primers and optimization of PCR conditions for detection of Cryptosporidium parvum and Giardia lamblia in water. Appl Environ Microbiol 1997; 63:106-14. [PMID: 8979344 PMCID: PMC168307 DOI: 10.1128/aem.63.1.106-114.1997] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Eight pairs of published PCR primers were evaluated for the specific detection of Cryptosporidium parvum and Giardia lamblia in water. Detection sensitivities ranged from 1 to 10 oocysts or cysts for purified preparations and 5 to 50 oocysts or cysts for seeded environmental water samples. Maximum sensitivity was achieved with two successive rounds of amplification and hybridization, with oligonucleotide probes detected by chemiluminescence. Primer annealing temperatures and MgCl2 concentrations were optimized, and the specificities of the primer pairs were determined with closely related species. Some of the primers were species specific, while others were only genus specific. Multiplex PCR for the simultaneous detection of Cryptosporidium and Giardia was demonstrated with primers amplifying 256- and 163-bp products from the 18S rRNA gene of Cryptosporidium and the heat shock protein gene of Giardia, respectively. The results demonstrate the potential utility of PCR for the detection of pathogenic protozoa in water but emphasize the necessity of continued development.
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Affiliation(s)
- P A Rochelle
- Water Quality Laboratory, Metropolitan Water District of Southern California, La Verne 91750-3399, USA.
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74
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Elagöz A, Abdi A, Hubert JC, Kammerer B. Structure and organisation of the pyrimidine biosynthesis pathway genes in Lactobacillus plantarum: a PCR strategy for sequencing without cloning. Gene 1996; 182:37-43. [PMID: 8982065 DOI: 10.1016/s0378-1119(96)00461-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This report describes the sequence and structural organisation of the pyrimidine biosynthesis pathway genes of Lactobacillus plantarum CCM 1904. It also describes an in vitro technique based on PCR for sequencing without cloning. This new technique was developed because it was impossible to clone certain parts of the L. plantarum genomic DNA in the Escherichia coli host. L. plantarum pyr genes are organised as a 9.8-kb operon with the following order: pyrR, pyrB, pyrC, pyrAA, pyrAB, pyrD, pyrF and pyrE. There are two major differences from the pyrimidine operons of Bacillus subtilis (Quinn et al., J. Bacteriol. 266 (1991) 9113-9127; Turner et al., J. Bacteriol, 176 (1994) 3708-3722) and Bacillus caldolyticus (Ghim et al., Microbiology 140 (1994) 479-491): the absence of pyrP encoding for uracil permease, and the absence of an open reading frame named orf2, whose function is unknown. Two mutually exclusive stem-loop structures were predicted at the 5'-end of L. plantarum pyr mRNA; this operon could be regulated by transcriptional attenuation under the control of PyrR. Complementation of E. coli pyrD, pyrF and pyrE mutants was obtained with a L. plantarum genomic DNA library. Alignment of the L. plantarum Pyr proteins with other known procaryotic Pyr proteins indicates that they display highly conserved regions in Gram-positive and Gram-negative bacteria.
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Affiliation(s)
- A Elagöz
- Laboratoire de Microbiologie et de Génétique de l'Université Louis-Pasteur, Unité de Recherche Associée au CNRS (URA No. D1481, Strasbourg, France
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75
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Rubin E, Levy AA. A mathematical model and a computerized simulation of PCR using complex templates. Nucleic Acids Res 1996; 24:3538-45. [PMID: 8836180 PMCID: PMC146141 DOI: 10.1093/nar/24.18.3538] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A mathematical model and a computer simulation were used to study PCR specificity. The model describes the occurrences of non-targeted PCR products formed through random primer-template interactions. The PCR simulation scans DNA sequence databases with primers pairs. According to the model prediction, PCR with complex templates should rarely yield non-targeted products under typical reaction conditions. This is surprising as such products are often amplified in real PCR under conditions optimized for stringency. The causes for this 'PCR paradox' were investigated by comparing the model predictions with simulation results. We found that deviations from randomness in sequences from real genomes could not explain the frequent occurrence of non-targeted products in real PCR. The most likely explanation to the 'PCR paradox' is a relatively high tolerance of PCR to mismatches. The model also predicts that mismatch tolerance has the strongest effect on the number of non-targeted products, followed by primer length, template size and product size limit. The model and the simulation can be utilized for PCR studies, primer design and probing DNA uniqueness and randomness.
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Affiliation(s)
- E Rubin
- Department of Plant Genetics, Weizmann Institute of Science, Rehovot, Israel
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76
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Haddad LA, Mingroni-Netto RC, Vianna-Morgante AM, Pena SD. A PCR-based test suitable for screening for fragile X syndrome among mentally retarded males. Hum Genet 1996; 97:808-12. [PMID: 8641701 DOI: 10.1007/bf02346194] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Ever since the identification of the genetic cause of fragile X syndrome as the expansion of an unstable trinucleotide sequence, several diagnostic strategies have evolved from molecular studies. However, we still lack a simple test suitable for population screening. We have therefore developed a nonisotopic polymerase chain reaction (PCR)-based technique for the identification of fragile X full mutations among men, with easy visualization of the PCR products on silver-stained polyacrylamide gels. The technique consists of PCR amplification with primers that flank the trinucleotide repeats, with a product of 557 bp for the (CGG)29 allele. Conditions were established such that full mutations failed to amplify and were thus identified with 98% sensitivity compared with Southern blot analysis. To produce an indispensable internal control we added to the reaction a third primer, internal to this fragment, allowing the multiplex amplification of a monomorphic band corresponding to a CG-rich stretch 147 bp upstream of the polymorphic region. In trials involving 41 patients and 74 controls, the PCR-based test here described showed specificity of more than 98.6%, accuracy of 99% and a sensitivity of 98%. Thus, although not suitable for medical diagnosis, it constitutes a useful tool for screening for the fragile X syndrome in populations of mentally retarded males.
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Affiliation(s)
- L A Haddad
- Departamento de Bioquímica, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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77
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Lick S, Keller M, Bockelmann W, Heller J. Rapid Identification of Streptococcus thermophilus by Primer-specific PCR Amplification Based on its lacZ Gene. Syst Appl Microbiol 1996. [DOI: 10.1016/s0723-2020(96)80012-9] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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78
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Sun YL, Tremblay J, Kong D, Hamet P. Candidate genes of hypertension with defective environmental expression. Cell Res 1995. [DOI: 10.1038/cr.1995.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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79
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Abstract
One of the most important factors affecting the quality of PCR is the choice of primers. In general, the longer the PCR product the more difficult it is to select efficient primers and set appropriate designing primers, and in general, the more DNA sequence information is available, the better the chance of finding an optimal primer pair. Efficient primers can be designed by avoiding the following flaws: primer-dimer formation, self-complementarity, too low Tm of the primers, and/or their incorrect internal stability profile. Tips on subcloning PCR products, calculating duplex stability (predicting dimer formation strength), and designing degenerate primers are given.
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Affiliation(s)
- W Rychlik
- National Biosciences Inc., Plymouth, MN 55447-5434, USA
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80
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Cheng S, Fockler C, Barnes WM, Higuchi R. Effective amplification of long targets from cloned inserts and human genomic DNA. Proc Natl Acad Sci U S A 1994; 91:5695-9. [PMID: 8202550 PMCID: PMC44063 DOI: 10.1073/pnas.91.12.5695] [Citation(s) in RCA: 456] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
We have used the polymerase chain reaction (PCR) to amplify up to 22 kb of the beta-globin gene cluster from human genomic DNA and up to 42 kb from phaga lambda DNA. We have also amplified 91 human genomic inserts of 9-23 kb directly from recombinant lambda plaques. To do this, we increased pH, added glycerol and dimethyl sulfoxide, decreased denaturation times, increased extension times, and used a secondary thermostable DNA polymerase that possesses a 3'-to 5'-exonuclease, or "proofreading," activity. Our "long PCR" protocols maintain the specificity required for targets in genomic DNA by using lower levels of polymerase and temperature and salt conditions for specific primer annealing. The ability to amplify DNA sequences of 10-40 kb will bring the speed and simplicity of PCR to genomic mapping and sequencing and facilitate studies in molecular genetics.
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Affiliation(s)
- S Cheng
- Department of Human Genetics, Roche Molecular Systems, Inc., Alameda, CA 94501
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81
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Chae KS, Murakawa K, Okubo K, Matsubara K. The use of overlapping and tailed short primers in the chromosomal assignment of short cDNAs by the polymerase chain reaction. Gene 1994; 142:199-205. [PMID: 8194752 DOI: 10.1016/0378-1119(94)90261-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
For the PCR-based chromosomal assignment of very short cDNA fragments specifically designed primers are required. We tested primers with very short core sequences that are identical or complementary to known cDNA sequences, with or without tails at the 5' ends. The lower limit of the core length for PCR using human chromosome templates was 14 nucleotides (nt) when they have tails. The minimal length of the tail was 2 nt when it was attached to the 5' end of a 14-nt core. In the absence of a tail, 15 nt are needed for the core to act properly. The overall size of the short cDNA fragments that could be assigned was further reduced by using a pair of primers that overlap at the 3' ends. The limits of the free energy of overlap were about -1.9 kcal/mol at 45 degrees C, -2.9 kcal/mol at 50 degrees C and -4.5 kcal/mol at 55 degrees C. A combination of these features in a primer pair allowed cDNA fragments as short as 30 nt to be assigned.
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Affiliation(s)
- K S Chae
- Institute for Molecular and Cellular Biology, Osaka University, Japan
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82
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Lin Q, Ma L, Burkhart W, Spremulli L. Isolation and characterization of cDNA clones for chloroplast translational initiation factor-3 from Euglena gracilis. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36900-4] [Citation(s) in RCA: 10] [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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83
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Pena SD, Barreto G, Vago AR, De Marco L, Reinach FC, Dias Neto E, Simpson AJ. Sequence-specific "gene signatures" can be obtained by PCR with single specific primers at low stringency. Proc Natl Acad Sci U S A 1994; 91:1946-9. [PMID: 8127912 PMCID: PMC43281 DOI: 10.1073/pnas.91.5.1946] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Low-stringency single specific primer PCR (LSSP-PCR) is an extremely simple PCR-based technique that detects single or multiple mutations in gene-sized DNA fragments. A purified DNA fragment is subjected to PCR using high concentrations of a single specific oligonucleotide primer, large amounts of Taq polymerase, and a very low annealing temperature. Under these conditions the primer hybridizes specifically to its complementary region and nonspecifically to multiple sites within the fragment, in a sequence-dependent manner, producing a heterogeneous set of reaction products resolvable by electrophoresis. The complex banding pattern obtained is significantly altered by even a single-base change and thus constitutes a unique "gene signature." Therefore LSSP-PCR will have almost unlimited application in all fields of genetics and molecular medicine where rapid and sensitive detection of mutations and sequence variations is important. The usefulness of LSSP-PCR is illustrated by applications in the study of mutants of smooth muscle myosin light chain, analysis of a family with X-linked nephrogenic diabetes insipidus, and identity testing using human mitochondrial DNA.
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Affiliation(s)
- S D Pena
- Núcleo de Genética Médica de Minas Gerais (GENE/MG), Belo Horizonte, Brazil
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84
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Vincent J, Gurling H, Melmer G. Oligonucleotides as short as 7-mers can be used for PCR amplification. DNA Cell Biol 1994; 13:75-82. [PMID: 8286042 DOI: 10.1089/dna.1994.13.75] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Amplification of DNA sequences using the polymerase chain reaction (PCR) requires as primers two oligonucleotides, which are carefully designed for length and G/C content. Such primers are generally between 18 and 30 bases long so that the primer sequences can amplify a unique sequence in the target genome; they should possess a minimal degree of secondary structure. We have tested the minimum length of G/C-rich and palindromic oligonucleotides to be used as primers in PCR. Oligonucleotides with sequences corresponding to the recognition sites of rare restriction enzymes were used on the DNA of vector constructs as model template DNA. Surprisingly, we found specific amplification with a low background over a wide range of temperatures for oligonucleotides as short as 7 nucleotides. This findings contradicts the previously reported empirical relationship between oligonucleotide length and ability to trigger amplification and points to the complex relationship between thermodynamic and kinetic criteria in relation to PCR. This technique should lead to new application in the cloning and screening of complex genomes.
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Affiliation(s)
- J Vincent
- Molecular Psychiatry Laboratory, University College London Middlesex School of Medicine, UK
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85
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Wirth M, Berthold E, Grashoff M, Pfützner H, Schubert U, Hauser H. Detection of mycoplasma contaminations by the polymerase chain reaction. Cytotechnology 1994; 16:67-77. [PMID: 7765790 DOI: 10.1007/bf00754609] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The polymerase chain reaction (PCR) has been used for the general detection of Mollicutes. 25 Mycoplasma and Acholeplasma species were detected including important contaminants of cell cultures such as M. orale, M. arginini, M. hyorhinis, M. fermentans, A. laidlawii and additional human and animal mycoplasmas. PCR reactions were performed using a set of nested primers defined from conserved regions of the 16S rRNA gene. The detection limit was determined to be 1 fg mycoplasma DNA, which is equivalent to 1-2 genome copies of the 16S rRNA coding region. The identity of the amplification products was confirmed by agarose gel electrophoresis and restriction enzyme analysis. DNA from closely and distantly related micro-organisms did not give rise to specific amplification products. The method presented here offers a much more sensitive, specific and rapid assay for the detection of mycoplasmas than the existing ones.
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Affiliation(s)
- M Wirth
- Genetik von Eukaryonten, GBF-Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany
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86
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Olsen DB, Wunderlich G, Uy A, Eckstein F. Direct sequencing of polymerase chain reaction products. Methods Enzymol 1993; 218:79-92. [PMID: 8389972 DOI: 10.1016/0076-6879(93)18010-a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- D B Olsen
- Merck Sharp and Dohme Research Laboratories, West Point, Pennsylvania 19486
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