The veil has finally been lifted on an enzyme that is critical to the process of DNA transcription and replication, and is a prime target of antibacterial and anticancer drugs. Researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and the University of California at Berkeley have produced the first three-dimensional structural images of a DNA-bound Type II topoisomerase (topo II) that is responsible for untangling coiled strands of the chromosome during cell division.