RNA Processing in an Escherichia coli Strain Deficient in Both RNase P and RNase III

Abstract

It is now evident that primary transcripts of most prokaryotic and eukaryotic RNAs contain extra regions of unknown function interspersed among regions destined to occur in mature molecules. The role of RNA processing enzymes is the correct removal of the extra regions leading to the formation of functional mature RNAs. The most intensively studied RNA processing reactions are those carried out by Escherichia coli RNase III (Robertson et al. 1968; Robertson and Dunn 1975; Dunn 1976), E. coli RNase P (Robertson et al. 1972; Stark et al. 1978), and Bacillus subtilis RNase M5 (Sogin et al. 1977; Meyhack et al. 1978). All three of these enzymes retain the ability to cleave their natural substrates properly in vitro, even following extensive purification of both the enzyme and the RNA precursor molecule.

It is difficult to identify and study the mechanism of various E. coli RNA processing enzymes without adopting a comprehensive approach that includes both the genetic and the biochemical definitions of a proposed RNA processing activity. This complication is evident in two of the approaches that have been recently employed to study this problem: several additional enzymatic activities that have been characterized biochemically from E. coli and tested on various RNA precursor substrates (Sakano and Shimura 1975; Schedl et al. 1976; Ghosh and Deutscher 1978) require further identification; in addition, mutations in well-characterized E. coli mutant strains lacking RNase III or RNase P and the resulting changes in RNA metabolism have been correlated with potential new RNA processing activities (Seidman...