Introduction to DNA Topoisomerases

The helical structure of duplex DNA allows for the faithful duplication and transmission of genetic information from one generation to the next, at the same time maintaining the integrity of the polynucleotide chains. The complementary nature of the two antiparallel DNA strands enables each to serve as a template for the synthesis of the respective daughter DNA strands. The intertwining of these polynucleotide chains in duplex DNA further ensures the integrity of the DNA helix by physically linking the individual strands in a structure stabilized by hydrogen bonding and stacking interactions between the hydrophobic bases. However, these same features pose a number of topological constraints that affect most processes involving DNA, such as DNA replication, transcription, and nucleosome assembly (reviewed in [1 –4 ]).