Control of ribosomal RNA synthesis in Escherichia coli. III. Cytoplasmic factors for ribosomal RNA synthesis.

The ribosomal RNA synthesis in a cell-free system containing the nucleoids and the cytoplasmic fraction prepared from Escherichia coli cells has been investigated. The addition of the "4S" fraction from the cytoplasm to the isolated nucleoids induces RNA synthesis by a new chain initiation. In this system a preferential initiation or rRNA chains occurs. The experimental results suggest that the 4S fraction contains at least two activities, one for releasing RNA-polymerases from the nucleoids, and another for the frequent initiation of rRNA chains. No restriction of the rRNA synthesis has been observed in the nucleoids and the 4S fraction from the amino acid-starved rel+ cells. The rRNA synthesized in the above system is detected at about 23S and 16S rRNA regions.