a1 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
In the mid-1950s, RNA was a somewhat mysterious molecule with unknown three-dimensional structure and little hard evidence of biological function. Changes began with the 1956 discoveries of the RNA double helix and the phenomenon of nucleic acid hybridization. Discovery of the DNA–RNA hybrid helix in 1960 opened the door to understanding biological information transfer. Single-crystal X-ray diffraction analysis made it possible to precisely define the RNA double helix, discover the novel L-shaped fold of transfer RNA (tRNA), and finally reveal the complete three-dimensional tRNA structure by 1974. By then, a functional understanding of protein synthesis had developed with an appreciation of the various roles of different RNA species. This was the era of RNA awakening.
c1 Author for correspondence: Dr. A. Rich, Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA. Tel.: 617-253-4715; Fax: 617-253-8699