Identification of a Novel RNA Molecule in a New RNA Processing

A temperature-sensitive mutant of Escherichia coli at the nonpermissive temperature fails to produce normal levels of 5 S rRNA. Instead, a number of larger RNA molecules are accumulated. One of these molecules, a 9 S RNA, contains 5 S rRNA sequences. When the strain is shifted from a nonpermissive to a permissive temperature, radioactive label is lost from the 9 S RNA and appears in 5 S rRNA. The identification of this 5 S rRNA-containing molecule indicates the participation of a new processing ribonuclease (RNase E) in the maturation of rRNA in E. coli. The 9 S RNA was not detected in a wild type strain, indicating that the processing step(s) involved in the formation of 5 S rRNA might be performed before the growing rRNA transcript is terminated.