Abstract
About the time we were finishing our graduate and postdoctoral work, study of RNA biochemistry was electrified by the discovery of RNA catalysts and the proposal of the RNA World hypothesis. The key initial observations were Tom Cech's discovery of the Tetrahymena rRNA self-splicing intron and the joint discovery by the labs of Norm Pace and Sid Altman that bacterial RNase P, the endonuclease that cleaves pre-tRNAs to give mature 5′ ends, was a trans-acting ribozyme. It soon became clear that the catalytic RNase P RNA subunit was widespread in Bacteria, largely from the work of Pace and colleagues. The excitement in the field was palpable over the notion that RNA (or something like it) was the primordial molecule, and many researchers immediately gravitated to the question of how much RNA catalysis survived in the modern world.