Specific inhibition of ribosomal RNA synthesis in vitro by guanosine 3′ diphosphate, 5′ diphosphate

Abstract

CONSIBERABLE evidence has accumulated that guanosine 3′-diphosphate, 5′-diphosphate (ppGpp)¹ is involved in the regulation of ribosomal RNA (rRNA) synthesis in Escherichia coli in vivo (see ref. 2). The involvement of ppGpp is most convincingly indicated by results obtained under conditions of amino acid starvation. A strong increase in ppGpp accumulation is always accompanied by a concomitant decrease in stable RNA accumulation³. In vitro, a specific effect of ppGpp has not been found, neither in a purified⁴, nor in a crude system⁵. Travers et al.^6,7 have proposed that ppGpp specifically affects rRNA synthesis by counteracting the effects of the protein elongation factor EF-Tu. Here, we show that ppGpp can specifically inhibit rRNA synthesis in vitro using purified RNA polymerase with two templates—DNA prepared by phenol extraction, and nucleoids prepared using methods developed by Pettijohn et al.⁸.