RNA catalysis and the origin of life.

Until the discovery of catalytic RNAs, first the self-splicing intron in Tetrahymena and then the bacterial RNAse P, cellular enzymes had always seemed to be protein in nature. The recognition that RNA can catalytically make and break phosphodiester bonds simplifies some of the assumptions required of a rudimentary self-replicating entity. Available information on the chemistry of RNA-catalyzed reactions is reviewed, with particular attention to self-splicing introns and tRNA processing by RNase P. An explicit model for a self-replicating RNA is described. The model postulates a nucleotide binding/polymerization site in the RNA, and takes advantage of intrinsic fluidity in RNA higher order structure to dissociate parent and progeny complementary strands.