Quantification of pyrophosphate as a universal approach to determine polymerase activity and assay polymerase inhibitors

Colorimetry-Based Phosphate Measurement for Polymerase Elongation

DNA detection, which includes the measurement of variants in sequences or the presence of certain genes, is widely used in research and clinical diagnosis. Both require DNA-dependent DNA polymerase-catalyzed strand extension. Currently, these techniques rely heavily on the instruments used to visualize the results. This study introduced a simple and direct colorimetric method to measure polymerase-directed elongation. First, pyrophosphate (PPi), a by-product of strand extension, is converted into phosphate (Pi). Phosphate levels were measured using either Mo-Sb or BIOMOL Green reagent. This study showed that this colorimetry can distinguish single-base variants and detect PCR products in preset stringent conditions, implicating the potential value of this strategy to detect DNA.

Polymerase assays for lead discovery: An overall review of methodologies and approaches

Polymerases represent an attractive molecular target for antibacterial drug development, antiviral intervention and cancer therapy. Over the past decade, academic groups and scientists from pharmaceutical industry have developed a large plethora of different functional assays to monitor the enzymatic reaction catalyzed by polymerases. These assays were used to enable high-throughput screening (HTS) for lead discovery purposes, as well as hit-to-lead (H2L) drug profiling activities. In both cases the choice of the assay technology is critical and to the best of our knowledge, there is no review available to help scientists to choose the most suitable assay. This review summarizes the most common functional assays developed to monitor the enzymatic activity of polymerases and discusses the advantages and disadvantages of each assay. Assays are presented and evaluated in term of cost, ease of use, high-throughput screening compatibility and liability towards delivering false positives and false negatives.

In vitro methods for testing antiviral drugs

Despite successful vaccination programs and effective treatments for some viral infections, humans are still losing the battle with viruses. Persisting human pandemics, emerging and re-emerging viruses, and evolution of drug-resistant strains impose continuous search for new antiviral drugs. A combination of detailed information about the molecular organization of viruses and progress in molecular biology and computer technologies has enabled rational antivirals design. Initial step in establishing efficacy of new antivirals is based on simple methods assessing inhibition of the intended target. We provide here an overview of biochemical and cell-based assays evaluating the activity of inhibitors of clinically important viruses.

An acid precipitation technique: A strip assay for the large-scale DNA polymerase activity screening

A new format of a very rapid, low-cost and high-productive analysis based on the acid precipitation of radiolabeled DNA was developed. By contrast to the conventional processing of a large number of GF/C discs, the method employs one GF/C strip containing samples on individual teeth. The strip assay was validated by comparison with the glass fiber disk technique; the efficiency was demonstrated by screening E. coli superproducers and fractions obtained at the steps of Bst DNA polymerase, Large Fragment purification by the protocol we developed. The principle proposed allows simultaneous assaying many samples for the activity of different polymerases.

A fluorescence polarization based assay for the identification and characterization of polymerase inhibitors

A homogenous fluorescence polarization (FP) assay was developed to monitor the enzymatic activity of polymerases. Under the optimized conditions established in this study, the assay provides highly robust and reproducible data. Miniaturization of the assay for high-throughput screening and compound testing was also performed. The sensitivity of the newly developed assay was confirmed using 2',3'-dideoxyadenosine-5'-triphosphate (ddATP), a chain-elongating inhibitor of the polymerase reaction. Side-by-side comparison of the presented fluorescence polarization assay with already well established PicoGreen® fluorescence intensity assay revealed that the performance of both formats is comparable with good assay sensitivity. However, the direct ratiometric readout of the presented FP assay makes it superior over existing colorimetric and fluorescence intensity based assays in terms of susceptibility to false positives. Moreover, due to its generic nature the presented FP assay can be applied to other polymerases and is compatible with identification of inhibitors and requirements of hit-to-lead programs.

Adapting capillary gel electrophoresis as a sensitive, high-throughput method to accelerate characterization of nucleic acid metabolic enzymes

Detailed biochemical characterization of nucleic acid enzymes is fundamental to understanding nucleic acid metabolism, genome replication and repair. We report the development of a rapid, high-throughput fluorescence capillary gel electrophoresis method as an alternative to traditional polyacrylamide gel electrophoresis to characterize nucleic acid metabolic enzymes. The principles of assay design described here can be applied to nearly any enzyme system that acts on a fluorescently labeled oligonucleotide substrate. Herein, we describe several assays using this core capillary gel electrophoresis methodology to accelerate study of nucleic acid enzymes. First, assays were designed to examine DNA polymerase activities including nucleotide incorporation kinetics, strand displacement synthesis and 3′-5′ exonuclease activity. Next, DNA repair activities of DNA ligase, flap endonuclease and RNase H2 were monitored. In addition, a multicolor assay that uses four different fluorescently labeled substrates in a single reaction was implemented to characterize GAN nuclease specificity. Finally, a dual-color fluorescence assay to monitor coupled enzyme reactions during Okazaki fragment maturation is described. These assays serve as a template to guide further technical development for enzyme characterization or nucleoside and non-nucleoside inhibitor screening in a high-throughput manner.