Role of the translocation factor G in the regulation of ribonucleic acid synthesis.

In an Escherichia coli rel(+)arg strain (ES-2) which carries a temperature-sensitive "G factor," the synthesis of ribonucleic acid (RNA) continues at the nonpermissive temperature (42 C) even though protein synthesis is terminated. However, at 32 C, the strain exhibits a stringent control of RNA synthesis in the absence of arginine. The stringent control of RNA synthesis imposed by trimethoprim (an inhibitor of initiation of protein synthesis) at 32 C is released at the nonpermissive temperature. Even the diauxie lag in RNA synthesis, which is regulated independently of the allelic state of the rel gene, is overcome by inactivation of the G factor. The unusual guanosine nucleotide, guanosine 5'-diphosphate 2' or 3'-diphosphate (ppGpp), is produced in small amounts during growth in strain ES-2. Withdrawal of arginine results in a greater accumulation of this compound at 32 C. At 42 C, the synthesis of ppGpp is abolished and is considerably lower than the level found in ES-2 under normal growth conditions. These results indicate that the translocation factor G plays an important role in the regulation of RNA synthesis and in the synthesis of ppGpp.