Z-DNA and Z-RNA: Methods-Past and Future.

A quote attributed to Yogi Berra makes the observation that "It's tough to make predictions, especially about the future," highlighting the difficulties posed to an author writing a manuscript like the present. The history of Z-DNA shows that earlier postulates about its biology have failed the test of time, both those from proponents who were wildly enthusiastic in enunciating roles that till this day still remain elusive to experimental validation and those from skeptics within the larger community who considered the field a folly, presumably because of the limitations in the methods available at that time. If anything, the biological roles we now know for Z-DNA and Z-RNA were not anticipated by anyone, even when those early predictions are interpreted in the most favorable way possible. The breakthroughs in the field were made using a combination of methods, especially those based on human and mouse genetic approaches informed by the biochemical and biophysical characterization of the Zα family of proteins. The first success was with the p150 Zα isoform of ADAR1 (adenosine deaminase RNA specific), with insights into the functions of ZBP1 (Z-DNA-binding protein 1) following soon after from the cell death community. Just as the replacement of mechanical clocks by more accurate designs changed expectations about navigation, the discovery of the roles assigned by nature to alternative conformations like Z-DNA has forever altered our view of how the genome operates. These recent advances have been driven by better methodology and by better analytical approaches. This article will briefly describe the methods that were key to these discoveries and highlight areas where new method development is likely to further advance our knowledge.