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Journal ArticleDOI

Polymerization behavior of Klenow fragment and Taq DNA polymerase in short primer extension reactions.

01 Oct 2010-Acta Biochimica et Biophysica Sinica (Oxford University Press)-Vol. 42, Iss: 10, pp 722-728

TL;DR: It was found that the longer the primer, the more efficient is the primer extension, and these polymerization behavior of short primers lay foundation about DNA polymerization mechanism and development of novel nucleic acid detection assays.

AbstractDNA polymerases amplify DNA fragments through primer extension reactions. However, polymerization behavior of short primers in the primer extension process has not been systematically explored. In this study, we examined the minimal primer length required for primer extension, and the effect of primer length, mismatches and other conditions on DNA polymerization using a non-radioactive method. Under the condition we conducted, the shortest primers polymerized by Klenow fragment (KF) and Taq DNA polymerase in our experiments were respectively heptamer and octamer. The extension efficiency was also affected by the up-stream overhanging structure of the primer-template complex. We hypothesized a simple model to interpret these observations based on the polymerase structures. Furthermore, it was found that the longer the primer, the more efficient is the primer extension. These polymerization behavior of short primers lay foundation about DNA polymerization mechanism and development of novel nucleic acid detection assays.

Topics: Primer extension (64%), Primer dimer (63%), Taq polymerase (62%), Primase (60%), Primer (molecular biology) (59%)

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Citations
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Journal ArticleDOI
TL;DR: Using lineage segregation in embryonic stem cell cultures as a model of early mammalian embryogenesis, DP-seq revealed novel sets of low abundant transcripts, some corresponding to the identity of cellular progeny before they arise, reflecting the specification of cell fate prior to actual germ layer segregation.
Abstract: We developed a novel Designed Primer-based RNA-sequencing strategy (DP-seq) that uses a defined set of heptamer primers to amplify the majority of expressed transcripts from limiting amounts of mRNA, while preserving their relative abundance. Our strategy reproducibly yielded high levels of amplification from as low as 50 picograms of mRNA while offering a dynamic range of over five orders of magnitude in RNA concentrations. We also demonstrated the potential of DP-seq to selectively suppress the amplification of the highly expressing ribosomal transcripts by more than 70% in our sequencing library. Using lineage segregation in embryonic stem cell cultures as a model of early mammalian embryogenesis, DP-seq revealed novel sets of low abundant transcripts, some corresponding to the identity of cellular progeny before they arise, reflecting the specification of cell fate prior to actual germ layer segregation.

38 citations


Journal ArticleDOI
TL;DR: The findings indicate that, as observed in humans, tandem or partially tandem duplications are the dominant form of insertion, although short duplications from ectopic donors account for a sizable fraction of insertions in rice (38%).
Abstract: The insertion of DNA into a genome can result in the duplication and dispersal of functional sequences through the genome. In addition, a deeper understanding of insertion mechanisms will inform methods of genetic engineering and plant transformation. Exploiting structural variations in numerous rice accessions, we have inferred and analyzed intermediate length (10–1,000 bp) insertions in plants. Insertions in this size class were found to be approximately equal in frequency to deletions, and compound insertion–deletions comprised only 0.1% of all events. Our findings indicate that, as observed in humans, tandem or partially tandem duplications are the dominant form of insertion (48%), although short duplications from ectopic donors account for a sizable fraction of insertions in rice (38%). Many nontandem duplications contain insertions from nearby DNA (within 200 bp) and can contain multiple donor sources—some distant—in single events. Although replication slippage is a plausible explanation for tandem duplications, the end homology required in such a model is most often absent and rarely is >5 bp. However, end homology is commonly longer than expected by chance. Such findings lead us to favor a model of patch-mediated double-strand-break creation followed by nonhomologous end-joining. Additionally, a striking bias toward 31-bp partially tandem duplications suggests that errors in nucleotide excision repair may be resolved via a similar, but distinct, pathway. In summary, the analysis of recent insertions in rice suggests multiple underappreciated causes of structural variation in eukaryotes.

35 citations


Cites background from "Polymerization behavior of Klenow f..."

  • ...The minimum primer length for extension for most polymerases in vitro appears to be 6 bp (19)....

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Journal ArticleDOI
TL;DR: A chip-based method to investigate polymerases and their interactions with nucleic acids is introduced, which employs an electrical actuation of DNA templates on microelectrodes and reveals previously unidentified tight binding states for Taq and Pol I (KF) DNA polymerases.
Abstract: The engineering of high-performance enzymes for future sequencing and PCR technologies as well as the development of many anticancer drugs requires a detailed analysis of DNA/RNA synthesis processes. However, due to the complex molecular interplay involved, real-time methodologies have not been available to obtain comprehensive information on both binding parameters and enzymatic activities. Here we introduce a chip-based method to investigate polymerases and their interactions with nucleic acids, which employs an electrical actuation of DNA templates on microelectrodes. Two measurement modes track both the dynamics of the induced switching process and the DNA extension simultaneously to quantitate binding kinetics, dissociation constants and thermodynamic energies. The high sensitivity of the method reveals previously unidentified tight binding states for Taq and Pol I (KF) DNA polymerases. Furthermore, the incorporation of label-free nucleotides can be followed in real-time and changes in the DNA polymerase conformation (finger closing) during enzymatic activity are observable.

25 citations


Journal ArticleDOI
TL;DR: A DNAzyme-based probe to detect the presence of telomerase in cell lysates with a fivefold increase in signal level for cancer cells over normal cells is described.
Abstract: Human telomerase is a polymerase enzyme that adds tandem repeats of DNA (TTAGGG) in the telomeric region to the ends of chromosomes. Since telomerase can be detected in immortalized, but not normal, somatic cells, it has been considered a selective target for cancer chemotherapy. Here, we describe a DNAzyme-based probe to detect the presence of telomerase in cell lysates. Telomerase elongates the primer site on the probe. Subsequent addition of the Pb(II) cofactor activates the DNAzyme, which cleaves the elongated fragment at the RNA site, releasing the probe for repetitive cycling and signal amplification. The cleaved fragment is detected by a reporter molecular beacon. Enzymatic amplification with rapid turnover allows detection of telomerase in the range of 0.1 to 1 μg cell lysate, with a fivefold increase in signal level for cancer cells over normal cells. This probe design can provide a simple, yet rapid and sensitive, measurement of telomerase activity.

23 citations


Journal ArticleDOI
TL;DR: A simple method to increase nucleotide diversity using single-stranded DNA (ssDNA) as a starting template and an efficient and convenient approach to generate diversity in nucleic acid based libraries, especially recombinant antibody libraries is described.
Abstract: Directed evolution of nucleotide libraries using recombination or mutagenesis is an important technique for customizing catalytic or biophysical traits of proteins. Conventional directed evolution methods, however, suffer from cumbersome digestion and ligation steps. Here, we describe a simple method to increase nucleotide diversity using single-stranded DNA (ssDNA) as a starting template. An initial PCR amplification using phosphorylated primers with overlapping regions followed by treatment with lambda exonuclease generates ssDNA templates that can then be annealed via the overlap regions. Double-stranded DNA (dsDNA) is then generated through extension with Klenow fragment. To demonstrate the applicability of this methodology for directed evolution of nucleotide libraries, we generated both gene shuffled and regional mutagenesis synthetic antibody libraries with titers of 2×108 and 6×107, respectively. We conclude that our method is an efficient and convenient approach to generate diversity in nucleic acid based libraries, especially recombinant antibody libraries.

18 citations


Cites background from "Polymerization behavior of Klenow f..."

  • ...This is important because the extension of KF is effective if the complementary region is longer than a heptamer (41)....

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References
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Journal ArticleDOI
26 Jun 1992-Science
TL;DR: A 3.5 angstrom resolution electron density map of the HIV-1 reverse transcriptase heterodimer complexed with nevirapine, a drug with potential for treatment of AIDS, reveals an asymmetric dimer.
Abstract: A 3.5 angstrom resolution electron density map of the HIV-1 reverse transcriptase heterodimer complexed with nevirapine, a drug with potential for treatment of AIDS, reveals an asymmetric dimer. The polymerase (pol) domain of the 66-kilodalton subunit has a large cleft analogous to that of the Klenow fragment of Escherichia coli DNA polymerase I. However, the 51-kilodalton subunit of identical sequence has no such cleft because the four subdomains of the pol domain occupy completely different relative positions. Two of the four pol subdomains appear to be structurally related to subdomains of the Klenow fragment, including one containing the catalytic site. The subdomain that appears likely to bind the template strand at the pol active site has a different structure in the two polymerases. Duplex A-form RNA-DNA hybrid can be model-built into the cleft that runs between the ribonuclease H and pol active sites. Nevirapine is almost completely buried in a pocket near but not overlapping with the pol active site. Residues whose mutation results in drug resistance have been approximately located.

1,873 citations


Journal Article
TL;DR: The rapid staining protocol significantly decreases the processing time required for silver-stained polyacrylamide gels, which is of particular importance in diagnostic situations, and allows individual bands from complex mixtures to be easily recovered for sequencing or probe preparation.
Abstract: A rapid silver-staining procedure for DNA fragments in polyacrylamide gels is described. The time required for band detection is 15 min and the limit of sensitivity 3 pg/mm2. PCR products subjected to this rapid staining protocol are readily recovered from the gel by excision and elution by incubation at 95 degrees C for 20 min. Bands of up to 3 kb have been recovered and reamplified from either recently prepared or dried gels. The rapid staining protocol significantly decreases the processing time required for silver-stained polyacrylamide gels, which is of particular importance in diagnostic situations. The recovery protocol allows individual bands from complex mixtures to be easily recovered for sequencing or probe preparation.

1,161 citations


Journal ArticleDOI
TL;DR: The effects of various primer-template mismatches on DNA amplification of an HIV-1 gag region by the polymerase chain reaction (PCR) were investigated, although the G:G mismatches appeared to be more sensitive to sequence context and dNTP concentrations than other mismatches.
Abstract: We investigated the effects of various primer-template mismatches on DNA amplification of an HIV-1 gag region by the polymerase chain reaction (PCR). Single internal mismatches had no significant effect on PCR product yield while those at the 3'-terminal base had varied effects. A:G, G:A, and C:C mismatches reduced overall PCR product yield about 100-fold, A:A mismatches about 20-fold. All other 3'-terminal mismatches were efficiently amplified, although the G:G mismatches appeared to be more sensitive to sequence context and dNTP concentrations than other mismatches. It should be noted that mismatches of T with either G, C, or T had a minimal effect on PCR product yield. Double mismatches within the last four bases of a primer-template duplex where one of the mismatches is at the 3' terminal nucleotide, in general, reduced PCR product yield dramatically. The presence of a mismatched T at the 3'-terminus, however, allowed significant amplification even when coupled with an adjacent mismatch. Furthermore, even two mismatched Ts at the 3'-terminus allowed efficient amplification.

1,024 citations


Journal ArticleDOI
TL;DR: Of particular interest are the role of editing in the fidelity of copying, the common enzymatic mechanism of polymerases, and the manners in which different domain structures function in the polymerase reaction in analogous ways.
Abstract: Possibly the earliest enzymatic activity to appear in evolution was that of the polynucleotide polymerases, the ability to replicate the genome accurately being a prerequisite for evolution itself. Thus, one might anticipate that the mechanism by which all polymerases work would be both simple and universal. Further, these enzymatic scribes must faithfully copy the sequences of the genome into daughter nucleic acid or the information contained within would be lost; thus some mechanism of assuring fidelity is required. Finally, all classes of polynucleotide polymerases must be able to translocate along the template being copied as synthesis proceeds. The crystal structures of numerous DNA polymerases from different families suggest that they all utilize an identical two-metalioncatalyzed polymerase mechanism but differ extensively in many of their structural features. From amino acid sequence comparisons (1) as well as crystal structure analyses (2), the DNA polymerases can be divided into at least five different families, and representative crystal structures are known for enzymes in four of these families. Perhaps the best studied of these families is the DNA polymerase I (pol I) or A polymerase family, which includes the Klenow fragments of Escherichia coli and a Bacillus DNA polymerase I, Thermus aquaticus DNA polymerase, and the T7 RNA and DNA polymerases, all of whose crystal structures are known (3–11). The second family of DNA-dependent DNA polymerases is DNA polymerase a (pol a) or B family DNA polymerase. All eukaryotic replicating DNA polymerases and the polymerases from phages T4 and RB69 belong to this family, and a crystal structure of the RB69 polymerase shows some similarities to the pol I family enzymes and numerous differences (12). Reverse transcriptases (RT), RNA-dependent RNA polymerases, and telomerase appear to show some common structural similarities, whereas the structure of DNA polymerase b shows no structural relatedness to any of these previous families (13, 14). On the basis of amino acid sequence comparisons but no crystal structures, it appears that the bacterial DNA polymerase III enzymes also form a family that is unrelated to the polymerases of known structure (1). Independent of their detailed domain structures, all polymerases whose structures are known presently appear to share a common overall architectural feature. They have a shape that can be compared with that of a right hand and have been described as consisting of “thumb,” “palm,” and “fingers” domains (15). The function of the palm domain appears to be catalysis of the phosphoryl transfer reaction whereas that of the fingers domain includes important interactions with the incoming nucleoside triphosphate as well as the template base to which it is paired. The thumb on the other hand may play a role in positioning the duplex DNA and in processivity and translocation. Although the palm domain appears to be homologous among the pol I, pol a, and RT families, the fingers and thumb domains are different in all four of these families for which structures are known to date (16). Here the functional and structural similarities and differences among the polymerases of known structure are explored. Of particular interest are the role of editing in the fidelity of copying, the common enzymatic mechanism of polymerases, and the manners in which different domain structures function in the polymerase reaction in analogous ways.

819 citations


Journal ArticleDOI
24 Jun 1994-Science
TL;DR: Two ternary complexes of rat DNA polymerase beta, a DNA template-primer, and dideoxycytidine triphosphate have been determined at 2.9 A and 3.6 A resolution, suggesting that the polymerase-DNA-ddCTP interactions are not affected by crystal packing forces.
Abstract: Two ternary complexes of rat DNA polymerase beta (pol beta), a DNA template-primer, and dideoxycytidine triphosphate (ddCTP) have been determined at 2.9 A and 3.6 A resolution, respectively. ddCTP is the triphosphate of dideoxycytidine (ddC), a nucleoside analog that targets the reverse transcriptase of human immunodeficiency virus (HIV) and is at present used to treat AIDS. Although crystals of the two complexes belong to different space groups, the structures are similar, suggesting that the polymerase-DNA-ddCTP interactions are not affected by crystal packing forces. In the pol beta active site, the attacking 3'-OH of the elongating primer, the ddCTP phosphates, and two Mg2+ ions are all clustered around Asp190, Asp192, and Asp256. Two of these residues, Asp190 and Asp256, are present in the amino acid sequences of all polymerases so far studied and are also spatially similar in the four polymerases--the Klenow fragment of Escherichia coli DNA polymerase I, HIV-1 reverse transcriptase, T7 RNA polymerase, and rat DNA pol beta--whose crystal structures are now known. A two-metal ion mechanism is described for the nucleotidyl transfer reaction and may apply to all polymerases. In the ternary complex structures analyzed, pol beta binds to the DNA template-primer in a different manner from that recently proposed for other polymerase-DNA models.

719 citations