Formation of all stable RNA species in Escherichia coli by posttranscriptional modification.

The kinetics of accumulation of the known stable RNA species (23S, 16S, and 5S rRNA and tRNA) in Escherichia coli C122 were monitored by polyacrylamide gel electrophoresis of purified cellular RNA, following termination of brief pulse labeling with (32)P-orthophosphate. Isotopically labeled stable RNA species appear only after a time lag, while total cellular RNA and the ostensible precursors to the stable RNA classes accumulate from the earliest times examined. It is concluded that all the known stable RNA species in E. coli are the products of posttranscriptional modification.