Synthesis of stable RNA by a stringent Escherichia coli strain during specific amino acid deprivation

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By definition amino‐acid starvation of an RCstrEscherichia coli strain causes simultaneous arrest of RNA and protein synthesis. However, it has recently been demonstrated that under such conditions mRNA synthesis does not stop and this result showed that RNA synthesis is not a coordinated process. The present study, which was carried out to determine the effects of amino‐acid starvation on net RNA synthesis in an RCstrE. coli strain, has led to the following results:a) during amino‐acid starvation net RNA synthesis is reduced to about 5% of the normal level;b) ribosomal RNA appears in 50 S and 30 S ribosomes and in 38 S and 21 S particles which seem to be precursors of 50 S and 30 S ribosomes, respectively;c) analysis by chromatography on methylated albumin column and by electrophoresis on polyacrylamide gels shows that the 38 S particle is devoid of 5 S RNA;d) a 5 S RNA appears in the supernatant fraction of ribosome preparations. This RNA, which is slightly different from the true 5 S RNA, is called 5 S stringent RNA. With respect to its chromatographic behaviour on G‐100 Sephadex and methylated albumin column, its mobility on disc electrophoresis, it is identical to 5 S relax RNA and 5 S chloromycetin RNA which are synthesized when protein synthesis is blocked either by amino‐acid starvation of a RCrelE. coli strain or by addition of chloromycetin;e) from the relative quantity of the different classes of RNA it is concluded that RNA synthesis is not coordinated and from the appearance of rRNA in ribosomal particles, a mechanism concerning the regulation of RNA synthesis is proposed.