Genetic studies of cleavage-initiated mRNA decay and processing of ribosomal 9S RNA show that the <em>Escherichia coli ams</em> and <em>rne</em> are the same.

We show in the present paper that the cleavages initiating decay of the ompA mRNA are suppressed both in the Escherichia coli ams^ts strain (originally defined by a prolonged bulk mRNA half-life) and in the rne^ts strain (originally defined by aberrant 9S RNA processing). The temperature-sensitive defects of both these strains are complemented by a recombinant lambda phage containing a genomic segment that carries the putative ams locus. A 5.8kb fragment from this genomic DNA segment was cloned into a low-copy plasmid and used to transform the ams^ts and rne^ts strains. This resulted in growth at the non-permissive temperature and a reoccurrence of the cleavages initiating decay of the ompA mRNA. Deletion analyses of this 5.8 kb fragment indicated that the putative ams open reading frame could complement both the Ams^ts and the Rne^ts phenotype with regard to the ompA cleavages. In addition we showed that the ams^ts strain suppresses 9S RNA processing to 5S RNA to the same extent as the rne^ts strain, and that the rne^ts strain has a prolonged bulk mRNA half-life, as was reported for the ams^ts strain. Therefore we suggest that ams and rne reflect the same gene locus; one which is involved both in mRNA decay and RNA processing. We discuss how this gene locus may related to the previously characterized endoribonucleolytic activities of RNase E and RNase K. [ABSTRACT FROM AUTHOR]