Preferential ribosomal RNA synthesis in the lysate of Escherichia coli

The RNA synthesis in non-viscous lysates containing the intact folded chromosome and cytoplasm fractions prepared from Escherichia coli has been examined in vitro. The RNA synthesis not only by chain extension but also by new chain initiation occurs in this system. While the RNA synthesis by chain extension takes place on the chromosome fraction alone (Pettijohn et al., 1970), an addition of the cytoplasm fraction is necessary for the synthesis by new chain initiations (de novo synthesis). Analyses of the in vitro synthesized RNA by hybridization-competition and by sucrose gradient centrifugation show that 16S and 23S ribosomal RNAs account for about 40% of the total RNA products. The cytoplasm fraction is required for the de novo synthesis of ribosomal RNA at high relative rate. Guanosine tetraphosphate (ppGpp) does not specifically inhibit ribosomal RNA synthesis in this system.