A Mn²⁺-dependent ribozyme

An RNA hairpin identical in sequence with the one formed during autocyclization of the 414-nucleotide Tetrahymena intervening sequence undergoes strand scission at a specific site in the presence of Mn²⁺. In addition to representing one of the smallest and simplest ribozymes possible, strand scission occurs readily under physiological conditions, is unaffected by the presence of Mg²⁺, and displays salt, pH, and temperature optima of potential use in exploiting Mn²⁺ as a regulatory switch in intact cells. The chemistry of strand scission of the RNA hairpin is described, as is the Mn²⁺-dependent solvolysis of a 231-nucleotide RNA transcript containing this structural motif.