Intrinsic Reactivity of DNA Secondary Structure

点击翻译按钮获取中文摘要

An accurate description of NA secondary structure must now include many conformations beyond those represented by a random coil or Watson-Crick double helix. Structural variants such as cruciform, hairpin, and hinged DNA along with the more transiently formed bulged or slipped sequences are often cited as the possible origin of mutational hotspots. Such aberrant conformations may adversely affect both the fidelity of DNA repair and the rate of nucleotide modification. This study has been designed to examine the molecular basis of this latter process by systematically evaluating the effect of duplex structure on the reactivity of DNA in a well defined model system. Photochemical modification of synthetic oligonucleotides serves as the primary method of derivatization and specifically, pyrimidine dimerization will be used to indicate the requirements of base mobility and orientation for DNA hyperreactivity. Kinetic and product analysis will determine the reaction efficiencies in helical and hairpin conformations containing mispaired or unpaired nucleotides. Concurrent chemical and enzymatic studies will generate a traditional and necessary context for interpreting the photochemical results. 1) Selective oxidation of DNA by KMnO4 will indicate the general accessibility of the thymine bases and 2) strand scission catalyzed by S-1 nuclease will demonstrate the related accessibilty of the sugar phosphate backbone.