Stanford Advisors


  • Eric Kool, Doctoral Dissertation Advisor (AC)

All Publications


  • Kinetic selection vs. free energy of DNA base pairing in control of polymerase fidelity PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Oertell, K., Harcourt, E. M., Mohsen, M. G., Petruska, J., Kool, E. T., Goodman, M. F. 2016; 113 (16): E2277-E2285

    Abstract

    What is the free energy source enabling high-fidelity DNA polymerases (pols) to favor incorporation of correct over incorrect base pairs by 10(3)- to 10(4)-fold, corresponding to free energy differences of ΔΔGinc∼ 5.5-7 kcal/mol? Standard ΔΔG° values (∼0.3 kcal/mol) calculated from melting temperature measurements comparing matched vs. mismatched base pairs at duplex DNA termini are far too low to explain pol accuracy. Earlier analyses suggested that pol active-site steric constraints can amplify DNA free energy differences at the transition state (kinetic selection). A recent paper [Olson et al. (2013)J Am Chem Soc135:1205-1208] used Vent pol to catalyze incorporations in the presence of inorganic pyrophosphate intended to equilibrate forward (polymerization) and backward (pyrophosphorolysis) reactions. A steady-state leveling off of incorporation profiles at long reaction times was interpreted as reaching equilibrium between polymerization and pyrophosphorolysis, yielding apparent ΔG° = -RTlnKeq, indicating ΔΔG° of 3.5-7 kcal/mol, sufficient to account for pol accuracy without need of kinetic selection. Here we perform experiments to measure and account for pyrophosphorolysis explicitly. We show that forward and reverse reactions attain steady states far from equilibrium for wrong incorporations such as G opposite T. Therefore,[Formula: see text]values obtained from such steady-state evaluations ofKeqare not dependent on DNA properties alone, but depend largely on constraints imposed on right and wrong substrates in the polymerase active site.

    View details for DOI 10.1073/pnas.1600279113

    View details for Web of Science ID 000374393800012

    View details for PubMedID 27044101

  • ATP-Releasing Nucleotides: Linking DNA Synthesis to Luciferase Signaling. Angewandte Chemie (International ed. in English) Ji, D., Mohsen, M. G., Harcourt, E. M., Kool, E. T. 2016; 55 (6): 2087-2091

    Abstract

    A new strategy is reported for the production of luminescence signals from DNA synthesis through the use of chimeric nucleoside tetraphosphate dimers in which ATP, rather than pyrophosphate, is the leaving group. ATP-releasing nucleotides (ARNs) were synthesized as derivatives of the four canonical nucleotides. All four derivatives are good substrates for DNA polymerase, with Km values averaging 13-fold higher than those of natural dNTPs, and kcat values within 1.5-fold of those of native nucleotides. Importantly, ARNs were found to yield very little background signal with luciferase. DNA synthesis experiments show that the ATP byproduct can be harnessed to elicit a chemiluminescence signal in the presence of luciferase. When using a polymerase together with the chimeric nucleotides, target DNAs/RNAs trigger the release of stoichiometrically large quantities of ATP, thereby allowing sensitive isothermal luminescence detection of nucleic acids as diverse as phage DNAs and short miRNAs.

    View details for DOI 10.1002/anie.201509131

    View details for PubMedID 26836342