Specific stimulation of ribosomal RNA synthesis in E. coli by a protein factor

Ribosomal RNA synthesis in a purified system is stimulated by a crude protein fraction prepared from E. coli. The positive effector which is not associated with RNA polymerase, nor is the sigma factor, increases the initiation frequency on rRNA operon. The additional rRNA synthesis in inhibited by ppGpp to the same extent as the basal one. The evidence presented points to the existence of a positive control element for rRNA synthesis, which activity depends upon the physiological state of the cell.